Through the final thesis, the application and importance of supplementary health insurance will be presented as one of the forms of supplementary protection against risks such as the risk of illness, injury and other accidents. Supplementary health insurance provides the insured with a greater scope of rights and a higher standard of health services than that covered by mandatory health insurance. Supplementary health insurance covers the difference up to the full amount of health care and treatment from compulsory health insurance, which are prescribed in the Law on Compulsory Health Insurance. There is a constant tendency for increased demand for contracting the number of supplementary health insurance policies, and the highest demand is recorded in the period from 2020 to today with the main driving factor, which is the emergence of Covid 19. Combining all the information, conclusions and considered facts that will be presented through the work itself, the main conclusions about the importance of supplementary health insurance will be made. The aim of this paper is to show the importance of supplementary health insurance as part of the security it provides to the insured in everyday life by clarifying the way insurance is implemented in the Croatian Institute for Health Insurance. The aim of the work is to explain its daily application, task and purpose in protecting human health during health care and to show how supplementary insurance contributes to reducing the risk that a person wants to cover. Also, the paper will compare the supplementary health insurance policy with the policy of the selected insurance company.