In SWT you must cleanup your allocated resources. Luckily the SWT Composite passed to you, is disposed by the framework so any Widget which you create on this control is disposed for you automatically.
Except Fonts, Colors and Images. For this you should, if possible use the JFace Local ResourceManager.
In case you try to find a resource leak you should have a look at The Sleak tool which allow you to track resource allocation.
