The pension insurance system represents one of the most important aspects of social insurance and as such is of great importance to the population. Among developed countries, including Croatia, there is a trend of population aging, which has long-term negative consequences for this form of insurance due to its implications for the basic assumptions of pension systems. This paper analyzes how the population aging factor affects the Croatian pension system, especially from the aspect of pension expenditures and pension adequacy. A projection was presented of the Croatian pension system until 2070 (from the perspective of current reforms) by the working group of the Committee for Economic Policy of the EU, which is reviewed through the part of public expenditures for pensions in the GDP. There are four driving forces of these expenditures, among which the aging of the population and the benefit ratio (the share of the average pension in the average salary) are interesting for analysis. The results show an increase in public spending on pensions in GDP in the first decade, then a gradual decrease, where population growth is the only factor affecting the growth of public spending. The compensation ratio suggests that low pensions will remain a permanent problem for Croatia, due to their continuous reduction by 10 p.p. from the aspect of the ratio to the average salary. However, the results do not show the analytics of public expenditures for pensions, i.e. they do not show the part that is not covered by contributions for pension insurance (and which is covered by the state budget).