We investigate the problem of exactly separating cover inequalities of maximum depth and we develop a pseudo-polynomial-time algorithm for this purpose. Compared to the standard method based on the maximum violation, computational experiments carried out on knapsack and multi-dimensional knapsack instances show that, with a cutting-plane method based on the maximum-depth criterion, we can optimize over the closure of the cover inequalities in a smaller number of cuts. These results encourage the research of efficient exact and heuristic separation algorithms based on maximizing the cut depth, also for other classes of valid inequalities.