This thesis presents the exceprional influence and analysis of the Croatian Pension Insurance Institute (hereinafter: the Institute) and its impact on the state budget. The pension insurance system is presented as a framework for exercising the right to a pension in the Republic of Croatia and an attempt was made to understand its impact on state finances through statistical dana and financial indicators. In order to gain an insight into the significant influence of the Institute on the state budget in a country that is aware of social sensitivity through various decisions that it helps one-off and shows this social awareness despite economic problems and problems of post-war recovery, and part of which is carried out by the Institute, in this thesis the regulations that are regarding the realization of the right to pension of special categories of insured persons and the more favorable realization of the right to pension of these categories os insured persons, which is particularlx significant whe it is known that the financing of the pension system is carried out through contributions from salaries and other sources of income and from the state budget. This thesis deals with a detailed analyzing the income and especially expenses of the Institute, which do not only concern the payment of contributions and the payment of pensions, but also faxtors that affect the state budget, which modernize and encourage the efficiency of the Institute's operations, and shows the impact of economic conditions, demographic trends, the application of international agreements on social security and other factors to the entire system and operations of the Institute that is, its income and wcpenses and ultimately the Institute's influence on the state budget.