There are various reasons that may explain why the designs of the EU and U.S. leniency programs and damage claims differ. In this note we discuss the welfare and deterrence implications of both designs as well as costs associated with each of the designs. We also show that there are substantial gaps between the design implied by economic theory and the way the main antitrust policy instruments are implemented in practice. The analysis implies that the U.S. system performs better in terms of deterrence and welfare criteria as well as in terms of increasing victims’ ability to obtain compensation. The EU system allows prosecutors to obtain more evidence through multiple leniency applications not disclosed to victims, which may increase the likelihood of conviction of the entire cartel and helps to save on investigation and litigation costs, at the price of lower fines and much lower expected damages, which in the absence of criminal sanction cast doubt on the possible deterrence effects.