One of the aspirations of the founders of the European Union was the unity of the European continent. Following the end of Soviet-type regimes in the late 1980s, the institutional machinery was put into action. However, this process has taken longer than expected, for different reasons: on one hand, because of the debate that commenced over the institutional consolidation and political construction of the existing Union, and on the other, because of the intensification of migration flows from the countries of the south and east. As a result of all of these factors, the incorporation of East European countries into the EU became dragged out over several years. As time passed, scepticism also grew in these countries as they saw that the inequalities between them and their western neighbours were becoming increasingly marked. Thus, a steady growth took place of economic migration flows from these countries into the EU, while the EU continued its negotiations with the countries of origin of these migrants. The process of EU enlargement to include Eastern Europe took place in two stages: the first, in May 2004, included Cyprus and Malta, as well as Hungary, Slovakia, Slovenia, the Czech Republic, Estonia, Latvia, Lithuania and Poland, while the second included only Romania and Bulgaria. This study deals with two issues that are of fundamental importance in any analysis of the different groups from Eastern and Central Europe that are present in Spain: the two moratoria on the free circulation of people imposed in 2004 and in 2007 (and their disastrous consequences) and the characteristics of these flows (when they arrived and why).