diff --git a/Applications/ExtApp/CMakeLists.txt b/Applications/ExtApp/CMakeLists.txt
index 44c8d9db6c..634c01bcf6 100644
--- a/Applications/ExtApp/CMakeLists.txt
+++ b/Applications/ExtApp/CMakeLists.txt
@@ -1,36 +1,40 @@
 project(ExtApp)
 
 set(_app_options)
 if(MITK_SHOW_CONSOLE_WINDOW)
   list(APPEND _app_options SHOW_CONSOLE)
 endif()
 
+MITK_USE_MODULE(qtsingleapplication)
+include_directories(${ALL_INCLUDE_DIRECTORIES})
+
 # Create a cache entry for the provisioning file which is used to export
 # the file name in the MITKConfig.cmake file. This will keep external projects
 # which rely on this file happy.
 set(MITK_EXTAPP_PROVISIONING_FILE "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/ExtApp.provisioning" CACHE INTERNAL "ExtApp provisioning file" FORCE)
 
 # Plug-ins listed below will not be
 #  - added as a build-time dependency to the executable
 #  - listed in the provisioning file for the executable
 #  - installed if they are external plug-ins
 
 set(_exclude_plugins
   org.blueberry.test
   org.blueberry.uitest
   org.mitk.gui.qt.application
   org.mitk.gui.qt.diffusionimagingapp
 )
 
 FunctionCreateBlueBerryApplication(
   NAME ExtApp
   DESCRIPTION "MITK - ExtApp Application"
   EXCLUDE_PLUGINS ${_exclude_plugins}
+  LINK_LIBRARIES ${ALL_LIBRARIES}
   ${_app_options}
 )
 
 # Add a build time dependency to legacy BlueBerry bundles.
 if(MITK_MODULES_ENABLED_PLUGINS)
   add_dependencies(ExtApp ${MITK_MODULES_ENABLED_PLUGINS})
 endif()
 
diff --git a/Applications/ExtApp/ExtApp.cpp b/Applications/ExtApp/ExtApp.cpp
index be576d189a..5da44004db 100644
--- a/Applications/ExtApp/ExtApp.cpp
+++ b/Applications/ExtApp/ExtApp.cpp
@@ -1,103 +1,117 @@
 /*=========================================================================
 
 Program:   Medical Imaging & Interaction Toolkit
 Language:  C++
 Date:      $Date$
 Version:   $Revision$
 
 Copyright (c) German Cancer Research Center, Division of Medical and
 Biological Informatics. All rights reserved.
 See MITKCopyright.txt or http://www.mitk.org/ for details.
 
 This software is distributed WITHOUT ANY WARRANTY; without even
 the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.  See the above copyright notices for more information.
 
 =========================================================================*/
 
 #include <application/berryStarter.h>
 #include <Poco/Util/MapConfiguration.h>
 
 #include <QApplication>
 #include <QMessageBox>
+#include <QtSingleApplication>
 
-class QtSafeApplication : public QApplication
+class QtSafeApplication : public QtSingleApplication
 {
 
 public:
 
-  QtSafeApplication(int& argc, char** argv) : QApplication(argc, argv)
+  QtSafeApplication(int& argc, char** argv) : QtSingleApplication(argc, argv)
   {}
 
   /**
    * Reimplement notify to catch unhandled exceptions and open an error message.
    *
    * @param receiver
    * @param event
    * @return
    */
   bool notify(QObject* receiver, QEvent* event)
   {
     QString msg;
     try
     {
       return QApplication::notify(receiver, event);
     }
     catch (Poco::Exception& e)
     {
       msg = QString::fromStdString(e.displayText());
     }
     catch (std::exception& e)
     {
       msg = e.what();
     }
     catch (...)
     {
       msg = "Unknown exception";
     }
 
     QString text("An error occurred. You should save all data and quit the program to "
                  "prevent possible data loss.\nSee the error log for details.\n\n");
     text += msg;
 
     QMessageBox::critical(0, "Error", text);
     return false;
   }
 
 };
 
+
 int main(int argc, char** argv)
 {
   // Create a QApplication instance first
   QtSafeApplication qSafeApp(argc, argv);
   qSafeApp.setApplicationName("ExtApp");
   qSafeApp.setOrganizationName("DKFZ");
 
+  // This function checks if an instance is already running
+  // and either sends a message to it (containing the command
+  // line arguments) or checks if a new instance was forced by
+  // providing the BlueBerry.newInstance command line argument.
+  // In the latter case, a path to a temporary directory for
+  // the new application's storage directory is returned.
+  QString storageDir = handleNewAppInstance(&qSafeApp, argc, argv, "BlueBerry.newInstance");
+
   // These paths replace the .ini file and are tailored for installation
   // packages created with CPack. If a .ini file is presented, it will
   // overwrite the settings in MapConfiguration
   Poco::Path basePath(argv[0]);
   basePath.setFileName("");
   
   Poco::Path provFile(basePath);
   provFile.setFileName("ExtApp.provisioning");
 
   Poco::Path extPath(basePath);
   extPath.pushDirectory("ExtBundles");
 
   std::string pluginDirs = extPath.toString();
 
   Poco::Util::MapConfiguration* extConfig(new Poco::Util::MapConfiguration());
+  if (!storageDir.isEmpty())
+  {
+    extConfig->setString(berry::Platform::ARG_STORAGE_DIR, storageDir.toStdString());
+  }
   extConfig->setString(berry::Platform::ARG_PLUGIN_DIRS, pluginDirs);
   extConfig->setString(berry::Platform::ARG_PROVISIONING, provFile.toString());
   extConfig->setString(berry::Platform::ARG_APPLICATION, "org.mitk.qt.extapplication");
 
   // Preload the org.mitk.gui.qt.ext plug-in (and hence also QmitkExt) to speed
   // up a clean-cache start. This also works around bugs in older gcc and glibc implementations,
   // which have difficulties with multiple dynamic opening and closing of shared libraries with
   // many global static initializers. It also helps if dependent libraries have weird static
   // initialization methods and/or missing de-initialization code.
   extConfig->setString(berry::Platform::ARG_PRELOAD_LIBRARY, "liborg_mitk_gui_qt_ext");
 
   return berry::Starter::Run(argc, argv, extConfig);
 }