We study the difference between the ex post and the ex ante perspectives in equality of opportunity (EOp). We show that the well documented conflicts between the compensation principles and various reward principles is but an aspect of a broader conflict between ex ante and ex post perspectives. The literature that takes the goal of providing equal opportunities as the guiding principle generally considers that this is clearly implemented only when, ex post, all individuals with the same effort obtain equal success. It is easy to believe that ex ante compensation is another natural embodiment of the same idea. In this paper we show that it is not.