The aim of this article is to discuss obstacles and success conditions for renewable energy sources in the EU-Accession States and to compare them with the framework in the EU-15. Besides the ten states which will join the EU in 2004, Bulgaria and Romania which will probably join in 2007 as well as Turkey are analysed. Most of these countries have had a century-long tradition in the utilisation of RES, primarily in biomass and hydropower. However, the communist regimes were convinced of the superiority of large-scale systems and converted the energy sectors into centralised units. Due to this dominating belief system more decentralised applications such as installations using renewable energies had to close. One crucial driving force for future renewable energy development in the Accession States comes from the stipulations set by the EU. The EU-Directive on the promotion of electricity produced from RES gives the new EU-members targets for their RES-development until 2010. Due to the Directive many Accession States have already begun to pay more attention to the topic and to introduce more systematic policies. Six of the Accession States have introduced minimum tariffs which were one of the main success conditions (besides a stable and sound investment programme as well as favourable background conditions) in the leading wind energy countries Germany and Spain. Beside the external pressure by the EU and other international obligations other driving forces such as the path dependencies in the national energy policies (degree of coal, oil and gas exploitation, nuclear power use, import dependency), the political support schemes for renewable energies, possibilities of obtaining external financial support and the cognitive environment are discussed. Finally similarities and differences between EU-15 and Accession States are worked out. (c) 2004 Elsevier Ltd. All rights reserved.