Parent can be any class that inherits from QObject. QWidgets are inherited from QObject, so yes.
If you create a dialog, give all member pointer variables the dialog as parent and you don't have to care about their memory
With Qt the memory handling is a lot easier than with blank c++.

PS: You could also take a look at QSharedPointer when using non-QObject classes. (or boost::shared_ptr if you don't like the Qt implementation)