EN
This article aims to present the concept of two-sided markets on the example of payment card systems, which have attracted the attention of regulatory and antitrust authorities in recent years. First, the paper offers a few insights into the basic economic theory behind two-sided markets. Second, it presents a brief description of payment card systems and their features. The following analysis focuses on arguments that speak in favour of a regulatory or antitrust intervention into payment card systems. Finally, some of the potential problems that antitrust authorities must face when assessing two-sided markets are presented on the basis of an assessment of the decisional practice of the UOKiK President and the European Commission.