Lately Croatian officials have received positive signs with regard to the progress of their country towards the EU membership. Nevertheless Croatia still needs to fulfil a number of conditions as required by the EU pre-accession conditionality method. This method is considered to be among the most successful foreign policy instruments the EU has implemented so far. During the last two enlargement processes, it proved itself to be able to align the post-communist candidate countries with the EU acquis communautaire. However EU conditionality has not been exempt from criticisms, many of them being related to its post-accession sustainability. The strength of the instrument lies primarily in the conditional membership incentive. Hence doubts arose with regard to the compliance of the new Member States with the EU acquis once the enlargement would be effective and the membership lever would disappear. Studies on post-accession compliance suggest that the dreaded ‘eastern problem’ remains rather theoretical and has not been observed in practice. Nevertheless in specific areas resting on the EU soft acquis the ‘eastern problem’ actually occurred. Empirical evidence backed up by international organisations’ reports notably demonstrated that the fight against corruption has experienced some backsliding in newly integrated Member States. The comparative study of the Slovene, Romanian, Bulgarian and Croatian experiences advocates for a distinction between hard acquis and soft acquis and establishes that a ‘Croatian problem’ similar to the ‘eastern problem’ is likely to occur as things stand at the present. Although the fight against corruption remains mostly under the scope of the Member States competences, the EU can have a substantial impact on the persistence of anti-corruption measures in Croatia and elsewhere if the organisation adjusts its current approach.