Competition authorities usually consider the introduction of leniency programs as a success story. The increased incentives to report on fellow cartelists due to the introduction of leniency is likely to have contributed substantially to the clear increase in the number of detected cartels. Critics argue that leniency programs primarily target weaker cartels, whereas the most profitable cartels stay undetected and may even benefit from a shift in the authority’s resources from active cartel screening to the handling of allegedly less important leniency applications. We show that this perception cannot be upheld in a numerical Bertrand competition model with heterogeneous products. In our approach, more profitable cartels consisting of producers of closer substitutes tend to be less stable. Thus leniency programs do in fact threaten more harmful cartels.