Index: trunk/src/org/openstreetmap/josm/data/validation/ValidationTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/ValidationTask.java	(revision 17850)
+++ trunk/src/org/openstreetmap/josm/data/validation/ValidationTask.java	(revision 17852)
@@ -1,4 +1,12 @@
 // License: GPL. For details, see LICENSE file.
 package org.openstreetmap.josm.data.validation;
+
+import static org.openstreetmap.josm.tools.I18n.tr;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import javax.swing.JOptionPane;
 
 import org.openstreetmap.josm.data.osm.OsmPrimitive;
@@ -6,4 +14,5 @@
 import org.openstreetmap.josm.gui.MainApplication;
 import org.openstreetmap.josm.gui.MapFrame;
+import org.openstreetmap.josm.gui.Notification;
 import org.openstreetmap.josm.gui.PleaseWaitRunnable;
 import org.openstreetmap.josm.gui.layer.ValidatorLayer;
@@ -11,10 +20,4 @@
 import org.openstreetmap.josm.gui.progress.swing.PleaseWaitProgressMonitor;
 import org.openstreetmap.josm.gui.util.GuiHelper;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
-
-import static org.openstreetmap.josm.tools.I18n.tr;
 
 /**
@@ -102,4 +105,14 @@
             }
         }
+
+        if (errors.stream().anyMatch(e -> !e.getPrimitives().stream().allMatch(OsmPrimitive::isDrawable))) {
+            final String msg = "<b>" + tr("Validation results contain elements hidden by a filter.") + "</b><br/>"
+                    + tr("Please review active filters to see the hidden results.");
+            GuiHelper.runInEDT(() -> new Notification(msg)
+                    .setDuration(Notification.TIME_LONG)
+                    .setIcon(JOptionPane.WARNING_MESSAGE)
+                    .setHelpTopic("Dialog/Validator")
+                    .show());
+        }
     }