Abstract: After the Yugoslavia had collapsed, the Balkan region became one of the most complex and heterogeneous in Europe. Countries, earlier united by Yugoslavia ended up in wars. This caused both political and economic problems; their solution may lie in the accession to the European Union (EU). At the same time, the EU is also not an ideal tool to solve its member countries’ problems: Greece can be considered as an example. Within the article, the authors set the task to answer the question: what scenario for former Yugoslavian countries’ economies will be realized if these countries enter into the EU. The major challenge of this article is to assess the effectiveness of the EU mechanisms without being affected by the high social role of the EU integration, so the authors concentrated on the economic factors. The authors answer the posed question and classify the former Yugoslavia’s countries; the authors also prove the low efficiency of the EU mechanisms in solving the economic and political contradictions of the countries, situated in the Balkan Peninsula. The major contribution of the article is the assertion that Slovenia and Croatia, despite being less involved in the Yugoslavian conflict, can become triggers for the negative effects transfer to the EU. It should be noted that the situation in the region is fragile and support of the countries of the former Yugoslavia from such an economically powerful association as the EU will lead to a worsening of the situation and destabilization.