I'm not an expert, but this is what Wikipedia has to say about it:

http://en.wikipedia.org/wiki/Thumb#Other_animals_with_opposable_digits


Primates

>Primates fall into one of four groups:
        Nonopposable thumbs: tarsiers and marmosets
        Pseudo-opposable thumbs: all strepsirrhines and Cebidae
        Opposable thumbs: Old World monkeys and all great apes
        Opposable with comparatively long thumbs: gibbons (or lesser apes)