The recent enlargement of the EU (since 2004) and the United Kingdom's decision to leave the European Union have prompted a growing research interest in the political and academic environment because of the causes and consequences of migration between the CEE countries and those in the Western Europe. In this study, the effects of European economic integration on the number of EU-15 immigrants from the newly integrated EU countries were assessed by econometric techniques. According to panel data models, in the period 2000-2015, the number of migrants from the new member states of the EU has increased, in average, with more than 2200 people only due to their EU membership. This result reflects the positive impact of European economic integration on the number of emigrants from the CEE countries that chose the EU-15 states as destination countries. Moreover, according to some ridge Bayesian regressions, during the period 2004-2015, the EU-15 immigrants coming from the EU-13 states did not negatively affect the economic growth of the EU-15 countries.