The chapter looks into the effectiveness of commitment decisions by reviewing selected examples from the European Commission’s jurisdiction. Proceedings with a considerable or often a very high degree of similarity in the air traffic, energy and payment-card industries provide useful insights into the extent to which the preceding decisions influence the behaviour of market participants and the approach taken by the Commission. The author concludes that commitment decisions are likely to be followed by other commitment decisions in similar cases and there is little evidence to suggest that market players voluntarily adjust their behaviour following a commitment case. A few recent examples suggest that this approach might not hold universally, leaving the actual impact of the commitment decisions challenging to forecast. It is argued that the limited deterrence and negative effect on legal certainty in the end limits the advantages of commitment decisions, as procedural efficiencies might evaporate if similar proceedings occur time after time. This, ultimately, may call into question the effectiveness of this tool, as practical examples suggest that the theoretical advantages are often not realised, while the negative effects on legal certainty and the limited deterrence effect are prominent.