Aim: There is no doubt that public authorities may be directly or indirectly involved in economic activity. A traditional way of distinguish state activity which is not subject to the rules of the market is to decide when the state acts as public authority. In case of state activity two category of situations should be distinguished: these where the state is engaged in an economic activity (sphere of dominium) and these when the state acts by exercising of public powers (sphere of imperium). In the opinion of the author of the article, the distinction between imperium and dominium is still relevant. According to the Competition and Consumer Protection Act of February 16, 2007, an entrepreneur is inter alia natural and legal person, as well as an organisational unit without a legal status to which legislation grants legal capacity, organising or providing public utility services which do not constitute economic activity in the meaning of the provisions on freedom of economic activity. The President of the Office of Competition and Consumer Protection found that public authorities exercising their administrative powers (sphere of imperium) may be classified as entrepreneurs. In the recent decisions which were subject of judicial review the President of UOKiK decided that the National Health Fund – a state authority responsible for organization and management of health care services in Poland – is an entrepreneur in the meaning of the Polish law (act on competition and consumer protection). The aim of this article is to answer the question whether competition rules should be applied to the state activity in the imperium sphere. This article will focus on the notion of an entrepreneur (undertaking) in polish and EU law in the context of the activity of the state. Design / Research methods: The objective of the article is achieved through doctrinal analysis of the relevant rules of the Polish and EU law and analysis of the recent decisions issued by the President of UOKiK, as well as judgments of the EU Courts, concerning the possibility of qualification of the widely understood state as an undertaking (entrepreneur).Conclusions / findings: From the analysis of the same concept applied in polish and EU law clearly follows that public entities acting ‘by exercising public power’ or ‘in their capacity as public authorities’ (imperium sphere) should not be classified as entrepreneurs (undertakings) in the meaning of competition law. The main scientific value added of the article are the conclusions that the provisions on the protection of competition should be applicable only to the activity of the state in the dominium sphere and that the definition of an entrepreneur and business (economic) activity should be connected to the existence of a market. Originality / value of the article: Paper should be interesting for public authorities, as well as for lawyers, dealing with problems concerning of qualification of public entities in the context of the competition law. The results of the research may be applied for example in the decisions that would be taken by the President of UOKiK. The consequences of application of the findings of the research to practice may be a change of approach to qualification of public entities in the context of the provision of competition law.