diff --git a/src/classes/PRunDataHandler.cpp b/src/classes/PRunDataHandler.cpp
index 6c92899e..8d136df2 100644
--- a/src/classes/PRunDataHandler.cpp
+++ b/src/classes/PRunDataHandler.cpp
@@ -2219,7 +2219,7 @@ Bool_t PRunDataHandler::ReadNexusFile()
   PRawRunDataSet dataSet;
   TString str;
   std::string sstr;
-  Int_t ival;
+  Int_t ival, idf{-1};
   Double_t dval, factor;
   bool ok;
 
@@ -2231,173 +2231,192 @@ Bool_t PRunDataHandler::ReadNexusFile()
       return true;
     }
 
-    // get header information
-
-    // get/set laboratory
-    sstr = "n/a";
-    if (nxs_file->HasDataset("/run/lab"))
-      sstr = nxs_file->GetDataset<std::string>("/run/lab").GetData()[0];
-    runData.SetLaboratory(sstr);
-
-    // get/set beamline
-    sstr = "n/a";
-    if (nxs_file->HasDataset("/run/beamline"))
-      sstr = nxs_file->GetDataset<std::string>("/run/beamline").GetData()[0];
-    runData.SetBeamline(sstr);
-
-    // get/set instrument
-    sstr = "n/a";
-    if (nxs_file->HasDataset("/run/instrument/name"))
-      sstr = nxs_file->GetDataset<std::string>("/run/instrument/name").GetData()[0];
-    runData.SetInstrument(sstr);
-
-    // get/set run title
-    str = "n/a";
-    if (nxs_file->HasDataset("/run/title"))
-      sstr = nxs_file->GetDataset<std::string>("/run/title").GetData()[0];
-    runData.SetRunTitle(sstr);
-
-    // get/set run number
-    ival = -1;
-    if (nxs_file->HasDataset("/run/number"))
-      ival = nxs_file->GetDataset<int>("/run/number").GetData()[0];
-    runData.SetRunNumber(ival);
-
-    // get/set temperature
-    dval = PMUSR_UNDEFINED;
-    sstr = "n/a";
-    if (nxs_file->HasDataset("/run/sample/temperature")) {
-      auto tmp_ds = nxs_file->GetDataset<float>("/run/sample/temperature");
-      dval = tmp_ds.GetData()[0];
-      if (tmp_ds.HasAttribute("units"))
-        sstr = std::any_cast<std::string>(tmp_ds.GetAttribute("units"));
-      if (sstr == "Celcius")
-        dval += 273.16;
+    // check for IDF_version
+    if (nxs_file->HasDataset("/run/IDF_version")) {
+      idf = nxs_file->GetDataset<int>("/run/IDF_version").GetData()[0];
+      std::cout << ">> PRunDataHandler::ReadNexusFile(): IDF V" << idf << std::endl;
     }
-    runData.SetTemperature(0, dval, 0.0);
-
-    // get/set field
-    dval = PMUSR_UNDEFINED;
-    sstr = "n/a";
-    factor = 1.0;
-    if (nxs_file->HasDataset("/run/sample/magnetic_field")) {
-      auto mag_ds = nxs_file->GetDataset<float>("/run/sample/magnetic_field");
-      dval = mag_ds.GetData()[0];
-      if (mag_ds.HasAttribute("units"))
-        sstr = std::any_cast<std::string>(mag_ds.GetAttribute("units"));
-      if (sstr == "Tesla")
-        factor = 1.0e4;
-    }
-    runData.SetField(dval*factor);
-
-    // get/set implantation energy
-    runData.SetEnergy(PMUSR_UNDEFINED);
-
-    // get/set moderator HV
-    runData.SetTransport(PMUSR_UNDEFINED);
-
-    // get/set RA HV's (LEM specific)
-    for (UInt_t i=0; i<4; i++)
-      runData.SetRingAnode(i, PMUSR_UNDEFINED);
-
-    // get/set setup
-    sstr = "n/a";
-    if (nxs_file->HasDataset("/run/notes"))
-      sstr = nxs_file->GetDataset<std::string>("/run/notes").GetData()[0];
-    runData.SetSetup(sstr);
-
-    // get/set sample
-    sstr = "n/a";
-    if (nxs_file->HasDataset("/run/sample/name"))
-      sstr = nxs_file->GetDataset<std::string>("/run/sample/name").GetData()[0];
-    runData.SetSample(sstr);
-
-    // get/set orientation
-    runData.SetOrientation("??");
-
-    // get/set time resolution (ns)
-    dval = PMUSR_UNDEFINED;
-    sstr = "n/a";
-    factor = 1.0;
-    if (nxs_file->HasDataset("/run/histogram_data_1/resolution")) {
-      auto res_ds = nxs_file->GetDataset<int>("/run/histogram_data_1/resolution");
-      dval = res_ds.GetData()[0];
-      if (res_ds.HasAttribute("units"))
-        sstr = std::any_cast<std::string>(res_ds.GetAttribute("units"));
-      if ((sstr == "picoseconds") || (sstr == "pico.seconds"))
-        factor = 1.0e-3; // ps -> ns
-    }
-    runData.SetTimeResolution(dval*factor);
-
-    // get/set start/stop time
-    sstr = "n/a";
-    TString date{"n/a"}, time{"n/a"};
-    if (nxs_file->HasDataset("/run/start_time"))
-      sstr = nxs_file->GetDataset<std::string>("/run/start_time").GetData()[0];
-    str = sstr;
-    SplitTimeDate(str, time, date, ok);
-    if (ok) {
-      runData.SetStartTime(time);
-      runData.SetStartDate(date);
-    }
-
-    sstr = "n/a";
-    date = "n/a";
-    time = "n/a";
-    if (nxs_file->HasDataset("/run/stop_time"))
-      sstr = nxs_file->GetDataset<std::string>("/run/stop_time").GetData()[0];
-    str = sstr;
-    SplitTimeDate(str, time, date, ok);
-    if (ok) {
-      runData.SetStopTime(time);
-      runData.SetStopDate(date);
-    }
-
-    // data with its metadata
-    int t0_bin{-1}, fgb{-1}, lgb{-1}, noOfHistos{-1}, histoLength{-1};
-    if (nxs_file->HasDataset("/run/histogram_data_1/counts")) {
-      auto count_ds = nxs_file->GetDataset<int>("/run/histogram_data_1/counts");
-      auto count = count_ds.GetData();
-      // get all necessary attributes
-      if (count_ds.HasAttribute("t0_bin"))
-        t0_bin = std::any_cast<int>(count_ds.GetAttribute("t0_bin"));
-      if (count_ds.HasAttribute("first_good_bin"))
-        fgb = std::any_cast<int>(count_ds.GetAttribute("first_good_bin"));
-      if (count_ds.HasAttribute("last_good_bin"))
-        lgb = std::any_cast<int>(count_ds.GetAttribute("last_good_bin"));
-      if (count_ds.HasAttribute("number"))
-        noOfHistos = std::any_cast<int>(count_ds.GetAttribute("number"));
-      if (count_ds.HasAttribute("length"))
-        histoLength = std::any_cast<int>(count_ds.GetAttribute("length"));
-      if (count.size() != noOfHistos*histoLength) {
-        std::cerr << std::endl << "**ERROR** nxH4::PNeXus data size error! count.size()=" << count.size() << ", #histos=" << noOfHistos << ", length=" << histoLength << "." << std::endl;
-        return false;
+    if (idf == -1) { // IDF_version not found
+      if (nxs_file->HasDataset("/raw_data_1/IDF_version")) {
+        idf = nxs_file->GetDataset<int>("/raw_data_1/IDF_version").GetData()[0];
+        std::cout << ">> PRunDataHandler::ReadNexusFile(): IDF V" << idf << std::endl;
       }
-      // fill dataSet
-      PDoubleVector data;
-      for (unsigned int i=0; i<noOfHistos; i++) {
-        dataSet.Clear();
-        dataSet.SetHistoNo(i+1); // i.e. histo numbers start with 1
-        dataSet.SetTimeZeroBin(t0_bin);
-        dataSet.SetFirstGoodBin(fgb);
-        dataSet.SetLastGoodBin(lgb);
-        for (unsigned j=0; j<histoLength; j++)
-          data.push_back(count[i*histoLength+j]);
-        dataSet.SetData(data);
-        runData.SetDataSet(dataSet);
-        data.clear();
-      }
-
-      // keep run name from the msr-file
-      runData.SetRunName(fRunName);
-
-      // keep the information
-      fData.push_back(runData);
-    } else { // no data found
-      std::cerr << std::endl << "**ERROR** nxH4::PNeXus couldn't obtain data: '/run/histogram_data_1/counts' is missing." << std::endl;
+    }
+    if ((idf != 1) && (idf != 2)) {
+      std::cerr << std::endl << ">> PRunDataHandler::ReadNexusFile(): a NeXus file with an invalid IDF V" << idf << std::endl;
       return false;
     }
 
+    if (idf == 1) { // HDF4 IDF V1
+      // get header information
+
+      // get/set laboratory
+      sstr = "n/a";
+      if (nxs_file->HasDataset("/run/lab"))
+        sstr = nxs_file->GetDataset<std::string>("/run/lab").GetData()[0];
+      runData.SetLaboratory(sstr);
+
+      // get/set beamline
+      sstr = "n/a";
+      if (nxs_file->HasDataset("/run/beamline"))
+        sstr = nxs_file->GetDataset<std::string>("/run/beamline").GetData()[0];
+      runData.SetBeamline(sstr);
+
+      // get/set instrument
+      sstr = "n/a";
+      if (nxs_file->HasDataset("/run/instrument/name"))
+        sstr = nxs_file->GetDataset<std::string>("/run/instrument/name").GetData()[0];
+      runData.SetInstrument(sstr);
+
+      // get/set run title
+      str = "n/a";
+      if (nxs_file->HasDataset("/run/title"))
+        sstr = nxs_file->GetDataset<std::string>("/run/title").GetData()[0];
+      runData.SetRunTitle(sstr);
+
+      // get/set run number
+      ival = -1;
+      if (nxs_file->HasDataset("/run/number"))
+        ival = nxs_file->GetDataset<int>("/run/number").GetData()[0];
+      runData.SetRunNumber(ival);
+
+      // get/set temperature
+      dval = PMUSR_UNDEFINED;
+      sstr = "n/a";
+      if (nxs_file->HasDataset("/run/sample/temperature")) {
+        auto tmp_ds = nxs_file->GetDataset<float>("/run/sample/temperature");
+        dval = tmp_ds.GetData()[0];
+        if (tmp_ds.HasAttribute("units"))
+          sstr = std::any_cast<std::string>(tmp_ds.GetAttribute("units"));
+        if (sstr == "Celcius")
+          dval += 273.16;
+      }
+      runData.SetTemperature(0, dval, 0.0);
+
+      // get/set field
+      dval = PMUSR_UNDEFINED;
+      sstr = "n/a";
+      factor = 1.0;
+      if (nxs_file->HasDataset("/run/sample/magnetic_field")) {
+        auto mag_ds = nxs_file->GetDataset<float>("/run/sample/magnetic_field");
+        dval = mag_ds.GetData()[0];
+        if (mag_ds.HasAttribute("units"))
+          sstr = std::any_cast<std::string>(mag_ds.GetAttribute("units"));
+        if (sstr == "Tesla")
+          factor = 1.0e4;
+      }
+      runData.SetField(dval*factor);
+
+      // get/set implantation energy
+      runData.SetEnergy(PMUSR_UNDEFINED);
+
+      // get/set moderator HV
+      runData.SetTransport(PMUSR_UNDEFINED);
+
+      // get/set RA HV's (LEM specific)
+      for (UInt_t i=0; i<4; i++)
+        runData.SetRingAnode(i, PMUSR_UNDEFINED);
+
+      // get/set setup
+      sstr = "n/a";
+      if (nxs_file->HasDataset("/run/notes"))
+        sstr = nxs_file->GetDataset<std::string>("/run/notes").GetData()[0];
+      runData.SetSetup(sstr);
+
+      // get/set sample
+      sstr = "n/a";
+      if (nxs_file->HasDataset("/run/sample/name"))
+        sstr = nxs_file->GetDataset<std::string>("/run/sample/name").GetData()[0];
+      runData.SetSample(sstr);
+
+      // get/set orientation
+      runData.SetOrientation("??");
+
+      // get/set time resolution (ns)
+      dval = PMUSR_UNDEFINED;
+      sstr = "n/a";
+      factor = 1.0;
+      if (nxs_file->HasDataset("/run/histogram_data_1/resolution")) {
+        auto res_ds = nxs_file->GetDataset<int>("/run/histogram_data_1/resolution");
+        dval = res_ds.GetData()[0];
+        if (res_ds.HasAttribute("units"))
+          sstr = std::any_cast<std::string>(res_ds.GetAttribute("units"));
+        if ((sstr == "picoseconds") || (sstr == "pico.seconds"))
+          factor = 1.0e-3; // ps -> ns
+      }
+      runData.SetTimeResolution(dval*factor);
+
+      // get/set start/stop time
+      sstr = "n/a";
+      TString date{"n/a"}, time{"n/a"};
+      if (nxs_file->HasDataset("/run/start_time"))
+        sstr = nxs_file->GetDataset<std::string>("/run/start_time").GetData()[0];
+      str = sstr;
+      SplitTimeDate(str, time, date, ok);
+      if (ok) {
+        runData.SetStartTime(time);
+        runData.SetStartDate(date);
+      }
+
+      sstr = "n/a";
+      date = "n/a";
+      time = "n/a";
+      if (nxs_file->HasDataset("/run/stop_time"))
+        sstr = nxs_file->GetDataset<std::string>("/run/stop_time").GetData()[0];
+      str = sstr;
+      SplitTimeDate(str, time, date, ok);
+      if (ok) {
+        runData.SetStopTime(time);
+        runData.SetStopDate(date);
+      }
+
+      // data with its metadata
+      int t0_bin{-1}, fgb{-1}, lgb{-1}, noOfHistos{-1}, histoLength{-1};
+      if (nxs_file->HasDataset("/run/histogram_data_1/counts")) {
+        auto count_ds = nxs_file->GetDataset<int>("/run/histogram_data_1/counts");
+        auto count = count_ds.GetData();
+        // get all necessary attributes
+        if (count_ds.HasAttribute("t0_bin"))
+          t0_bin = std::any_cast<int>(count_ds.GetAttribute("t0_bin"));
+        if (count_ds.HasAttribute("first_good_bin"))
+          fgb = std::any_cast<int>(count_ds.GetAttribute("first_good_bin"));
+        if (count_ds.HasAttribute("last_good_bin"))
+          lgb = std::any_cast<int>(count_ds.GetAttribute("last_good_bin"));
+        if (count_ds.HasAttribute("number"))
+          noOfHistos = std::any_cast<int>(count_ds.GetAttribute("number"));
+        if (count_ds.HasAttribute("length"))
+          histoLength = std::any_cast<int>(count_ds.GetAttribute("length"));
+        if (count.size() != noOfHistos*histoLength) {
+          std::cerr << std::endl << "**ERROR** nxH4::PNeXus data size error! count.size()=" << count.size() << ", #histos=" << noOfHistos << ", length=" << histoLength << "." << std::endl;
+          return false;
+        }
+        // fill dataSet
+        PDoubleVector data;
+        for (unsigned int i=0; i<noOfHistos; i++) {
+          dataSet.Clear();
+          dataSet.SetHistoNo(i+1); // i.e. histo numbers start with 1
+          dataSet.SetTimeZeroBin(t0_bin);
+          dataSet.SetFirstGoodBin(fgb);
+          dataSet.SetLastGoodBin(lgb);
+          for (unsigned j=0; j<histoLength; j++)
+            data.push_back(count[i*histoLength+j]);
+          dataSet.SetData(data);
+          runData.SetDataSet(dataSet);
+          data.clear();
+        }
+
+        // keep run name from the msr-file
+        runData.SetRunName(fRunName);
+
+        // keep the information
+        fData.push_back(runData);
+      } else { // no data found
+        std::cerr << std::endl << "**ERROR** nxH4::PNeXus couldn't obtain data: '/run/histogram_data_1/counts' is missing." << std::endl;
+        return false;
+      }
+    } else { // HDF4 IDF V2
+      // not yet implemented
+    }
 #endif
   } else { // HDF5
     std::unique_ptr<nxH5::PNeXus> nxs_file = std::make_unique<nxH5::PNeXus>(fRunPathName.Data());
@@ -2405,13 +2424,31 @@ Bool_t PRunDataHandler::ReadNexusFile()
       std::cerr << std::endl << "**ERROR** allocation of nxH5::PNeXus object failed." << std::endl;
       return true;
     }
+
+    // check for IDF_version
+    if (nxs_file->HasDataset("/run/IDF_version")) {
+      idf = nxs_file->GetDataset<int>("/run/IDF_version").GetData()[0];
+      std::cout << ">> PRunDataHandler::ReadNexusFile(): IDF V" << idf << std::endl;
+    }
+    if (idf == -1) { // IDF_version not found
+      if (nxs_file->HasDataset("/raw_data_1/IDF_version")) {
+        idf = nxs_file->GetDataset<int>("/raw_data_1/IDF_version").GetData()[0];
+        std::cout << ">> PRunDataHandler::ReadNexusFile(): IDF V" << idf << std::endl;
+      }
+    }
+    if ((idf != 1) && (idf != 2)) {
+      std::cerr << std::endl << ">> PRunDataHandler::ReadNexusFile(): a NeXus file with an invalid IDF V" << idf << std::endl;
+      return false;
+    }
+
+    if (idf == 1) { // HDF5 IDF V1
+      // not yet implemented
+    } else { // HDF5 IDF V2
+      // not yet implemented
+    }
   }
 
 /* //as35
-  if (nxs_file->GetIdfVersion() == 1) {
-
-    // keep the information
-    fData.push_back(runData);
   } else if (nxs_file->GetIdfVersion() == 2) {
     if (!nxs_file->IsValid()) {
       std::cout << std::endl << "**ERROR** invalid NeXus IDF 2 version file found." << std::endl;