Commission for Protection of Competition, in cooperation with the Chamber of Commerce of Serbia, seeks to promote competition policy in Serbia. With regard to that, representatives of Commission for Protection of Competition participated, as lecturers, at the seminar held in the Serbian Chamber of Commerce organized in cooperation with that institution within the Project for Strengthening the Competition in Serbia financed by EU, which is a part of program for enhancement of competition policy in the Republic of Serbia, and implemented by German Agency for International Cooperation (GIZ). Mr. Milan Kostic spoke about methodology of determining the relevant market, while the role and practice of the Commission for Protection of Competition was presented by Mr.Nebojsa Milenkovic. Mr.Andrej Plahutnik discussed the assessment of effective competition and restrictions, prohibited constraints and importance of determining relevant market.