Because of the specificity of the medical profession, the scope of responsibility and the adverse consequences that often arise in carrying out the healthcare activity, the legislator prescribes the obligation to conclude a medical insurance contract of professional liability. The contract on the professional liability of a physician is the contract that the employer has to make for his employees with the insurance company. In this type of contract, the employer or the insurance contractor is usually the hospital or other health institution, and it is in accordance with Art. 124. 4. of the Health Care Act that is obliged to conclude such a contract with the insurer. However, the obligation prescribed by the said article is only formal and in practice still rare, which will be further discussed below. The focus of this paper is the insurance contract for professional liability of doctors, the definition of professional activity as such and the conditions for the liability of a doctor. Particular emphasis is placed on the definition of a professional person and the circle of persons covered by that term. The topic of the graduate thesis is also current in Croatia everyday, given that Croatia, by joining the European Union, has assumed the obligation to legislate and harmonize the responsibilities of professionals, but it has not yet been fully implemented. The topic was dealt by the reference to professional literature, applicable regulations, review of comparative law, and review of court practice. Particularly interesting is the question of how to determine the responsibilities of a doctor, as there are different attitudes in different legal systems. This paper deals with basic concepts and elements of the insurance contract with reference to the same in the insurance contract of the professional liability of the physician. With a detailed analysis of Croatian legislation related to this issue, the paper analyzes the regulation of the concept of professional responsibility of doctors in other European countries.