How can I configure the font size for the tree item in the package explorer/outline in Eclipse?
Which item in Font under Preferences I should change?
This answer applies to Mac OS X user. Tested with Mavericks (10.9.2) but should work in all versions.
As stated before in previous answers, to change the font size in package explorer you need to change system font size. The problem here is to do exactly this. My solution:

The results:

Happy coding!