Accession appears to be both a blessing and a curse to transition countries. On the one hand, EU membership supports their transformation from authoritarian regimes with centralized planning economies into liberal democracies with market economies. On the other hand, the accession countries face great difficulties in restructuring their economic and political institutions in order to meet the conditions for EU membership. The systematic involvement of non-state actors in the adoption of and adaptation to EU requirements was thought to be a remedy for the problems of European Enlargement towards ‘weak’ transition countries. Companies and civil society organizations could provide the governments of the accession countries with important resources (money, information, expertise and support) that are necessary to make EU policies work. The article explores the role of non-state actors in governing the double challenge of transition and accession. Focusing on the field of environmental policy, we seek to find out to what extent accession has empowered non-state actors by giving them a voice in the adoption of and adaptation to the EU's green acquis. Our study on the implementation of EU environmental policies in Poland, Hungary and Romania shows that accession left little room for the involvement of non-state actors into the policy process. The article argues that both state and non-state actors in transition countries were often too weak to make cooperation work during the accession period. The double weakness of transition countries and a political culture hostile to public involvement seriously constrained the empowering of non-state actors by ‘Europeanization through accession’.