The article aims to answer the question of whether and when publicly owned establishments are allowed to conduct economic activity. The concepts of economic activity and publicly owned establishment are explained. The author points out that publicly owned establishments are not fully free to undertake business activity but must fulfil certain conditions to be able to do so. By discussing the case of museums, the author considers the options and forms of possible economic activity. It was emphasized that the economic activity carried out by a museum must be of an auxiliary nature and should not be focused on profit-making only but should, in the first place, help execute the mission of public administration.