Apes have a number of unique traits that distinguish them from Cercopithecoids, including

Hi

With a little bit of research, I found the following:

Cercopithecoids have a narrow nose and palate, and smaller brains relative to body size than Hominoids.
Cercopithecoids' molars are bilophodont (two cusps) but Hominoids' have several cusps.
Cercopithecoids have tails (often long), while Hominoids have no tails.
Cercopithecoids are laterally compressed, with a narrower thorax and pelvis, and a longer trunk. Compare this to hominoids like the gorillas, who are pretty wide in the chest.
Cercopithecoids' back legs are at least as long as or longer than their front legs, while Hominoids tend to have longer arms than legs.

Hope this helps