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.