The European Union is confronted with the biggest enlargement in its history: ten states, among them eight middle European - the so called "buffer zone" in the new European migration landscape - will become members in 2004. Other candidates hope to join in the coming years. For all Eastern and Eastern European countries, including those that are not candidates, the end of the bi-polar world meant a hope of "return to Europe". When shifting its borders to the East, the European Union both includes and excludes. The final objective to achieve Europe as "a space of freedom, security and justice", is conditioned by the capacity and necessity to control the migratory flows. The prospect of free circulation for the citizens of the new Union members entails also fears: the EU countries are afraid of the consequences the enlargement would have on migratory flows from the countries of the Central and Eastern Europe and which transit through that area. The perception of migrants as a threat inspired the conditions that the Union imposed on the candidate countries concerning migration policy issues and which mostly focus on the protection of its Eastern borders. For the future Union members however, protecting of the thousand of kilometers of their Eastern border, implies a number of quite different problems. These countries are afraid of the impact the restrictive measures they are obliged to implement would have both on many economic and family ties which have been maintained since the socialist period and on more recently engaged cooperation with the neighbours which are not candidates. The challenge of enlargement is different therefore for the EU members, for the candidate countries and for those who are for the moment excluded from the process. The fears do not seem to be always grounded. Thus, the impact of enlargement which, it was feared, could have been so destabilizing for the Union because of potentially large migration flows, is more likely to be destabilizing for the new candidate countries, especially concerning their relations with their neighbours excluded from the enlargement process.