The correct grasp of objects is a key aspect for the right fulfilment of several tasks. In robotics, the development of grippers more and more complex and versatile, such as mechanical hands, increases the necessity of algorithms to automatically determine the grasps, and, simultaneously, arises the need to evaluate the quality of the grasps in order to optimize them. This work presents a review of the quality measures proposed in the literature to quantify the grasp quality. The quality measures are classified into two main groups according to the main considered aspect: the location of the contact points on the object surface or the hand configuration. Approaches that combine different quality measures from the two previous groups to obtain global quality measures are also discussed.