Conditional Custom Editor with Popup

I'm trying to show different behavior in my custom editor when selecting an option from a Popup. I used BeginChangeCheck() and EndChangeCheck() to avoid checking the Popup continuously. The problem is that anything GUI related is not shown in Editor then. Any tips on this?

This little example illustrates the problem (I used LabelField elements to keep it simple, but in my code I'm using several Popup and MaskField elements inside each if branch).

 EditorGUI.BeginChangeCheck();
 selected=EditorGUILayout.Popup(selected,options);
 if(EditorGUI.EndChangeCheck())
     {
     if (selected==0)
         {
         EditorGUILayout.LabelField("You selected first item");  // Does not work
         Debug.Log("You selected first item");  // Works
         }
     else if (selected==1)
         {
         EditorGUILayout.LabelField("You selected second item");  // Does not work
         Debug.Log("You selected second item");  // Works
         }
     }