Aim: The notion of a public interest in administrative law science and in the administration science occupies the central position in the notion chart. Consequently, it is also the main notion of public protection of competition. The legislator has not decided to present a definition of "the public interest" in the Competition and Consumer Protection Law Act. As a result, interpretation of the concept is largely dependent on the judicature. The aim of the paper is to analyse the notion of a public interest and its interpretation both in science and in practice of law application. Design / Research methods: The author's conclusions are based on analysing the pubic interest interpretation made by representatives of the doctrine and the judicature. Conclusions / findings: In consequence, the author is of very good opinion on how the notion of a public interest in the public protection of competition evolves, adapting to the current social and market condition and to the development of the competition law science. Originality / value of the article: Originality of the topic comes from the legal analysis of the controversial presentation of a correctly operating competition on the medicinal product sales market, unprecedented in the judicature, as a mechanism allowing patients to obtain health services in line with the current status of medical knowledge.