The paper is a theoretical study on relations between economic regulation and competition law. Based on the classical welfare economics doctrine, it starts with a presentation of premises and aims of the discussed parts of legislation, such as market failures and market optimisation. The roles of economic regulation and competition law and their complementarity are analysed. This is followed by an examination of norms of substantive law in the deliberated areas. Distinguished are features such as sectoral or cross-sectoral scope of norms, their repressive or prescriptive function, their reactive or proactive nature and ex ante or ex post effects and their relation to competition (regulation of competition or regulation for competition). Lastly, the paper points to instances of convergence of economic regulation and competition law.