I am not sure what you are seeing now. What you could try is:

1. explicitly set the delegate to use QStyledItemDelegate for the tree. If that doesn’t work:
2. also set a style sheet for QTreeView::item, where you can set the background property to a Qt::LinearGradientPattern with the right colors.

Thanks Andre
I emulated the look using the following stylesheet

Please have a look at the Mac Main Window Demo [developer.qt.nokia.com] – it shows how to create main window applications that has the same appearance as other Mac OS X applications, including customizing the item view, the splitter and a search field and should be exactly what you need

Thanks Volker! That article is truly helpful!