Considering the illegal markets in the European Union member states, the valences of drug trafficking get more and more worrisome, both of the proliferation level, and the size of the financial transactions, the European markets being the most profitable in terms of heroin and cocaine consumption. The article focuses on the analysis of the theoretical aspects concerning the EU illegal drug markets, for identifying and understanding their peculiarities. In this context, we will emphasize the characteristics and dynamics of these markets, their national and european economic mechanisms, the profits made by organized crime networks and also, the impact of these activities on the formal economy.