The thesis presents a complex analysis of the social security system in the European Union with a special emphasis on the pension systems, or better, their coordination. The existing level of pension systems coordination has been a result of a long development process that is reflected in a sophisticated legislation. The thesis also introduces a case study in which an individual has gained a working experience from five EU countries and applies for the retirement pension in the last of these countries. This case study has been prepared in order to review the overall pension system functionality as well as to demonstrate its weeknesses. In the final part of the thesis, the author summarizes his recent conclusions and finds the EU system to b...