Abstract Unlike in the case of legislative acts, retroactive effect of court decisions does not at first glance constitute a legal problem. However, the retroactive effect of court decisions becomes a problem when other cases, such as parallel cases which were not the subject of the original court decision, are affected and these questions become even more precarious in the context of decisions reviewing legislation due to an erga omnes (de iure or de facto as precedents) effect. The article aims to provide a reappraisal of the problem of the retroactive effect of decisions of the European Court of Justice against the backdrop of recent cases (particularly the dogmatically significant decisions ''Meilicke'' and ''Banco Popolare di Cremona'' both focusing on tax issues in 2006), taking into account the Courts jurisprudence to date, the normative basis in the EC Treaty as well as the diverse Member States' traditions and experiences. By way of conclusion the study advocates the limitation of the retroactive effect of decisions of the European Court of Justice in certain cases against the background of the protection of legal certainty and its sub–category of legitimate expectations. In particular in cases where unforeseen and in aggregate very substantial pecuniary obligations of the Member States vis–a–vis their citizens are at issue, a balancing approach in applying the retroactive effect of judgements, as yet insufficiently explored, appears to be called for.