The aim of the present study is to review the definitions of the enterprises in the European Union, Western Balkans and Kosovo. The study also proposes the classification and comparison of small, medium-sized and large enterprises in the European Union, Western Balkan countries, such as Albania, Montenegro, Macedonia, Croatia, Bosnia and Herzegovina, Serbia, and in Kosovo. The study has been performed using the legal, economic, comparative and practice methodology. The results of the study suggest that states should have control over the categorization of enterprises, so the enterprises with higher economic power cannot have the opportunity to hurt those with lesser economic power, all based on the regulation law and its implementation in practice.