The pension system in the Republic of Croatia, as it exists today began operating in 2002. Over the years it has evolved and improved, but its core structure consists of three pillars of pension insurance. The first pillar is based on the principle of intergenerational solidarity and is mandatory for all employed persons. The Croatian Pension Insurance Institute is responsible for regulating the first pillar. The second pillar, also known as mandatory pension insurance, based on individual capitalized savings is designed to enhance future pensions through investments made with the funds in the user's account. This pillar is also mandatory for all employed persons. The Central Registry of Insured Persons (REGOS) is responsible for the proper functioning of the second pillar. The third pillar is called voluntary pension insurance based on individual capitalized savings. Unlike the second pillar, the third pillar is voluntary and contributions to it are financially incentivized by the state. There are open voluntary pension funds where all citizens can save, while closed voluntary pension funds are available only to employees of the fund's founding employer. The institution responsible for overseeing both the third and second pillars is Hanfa. Pension insurance companies are responsible for paying out pensions, both voluntary and mandatory, and two pension insurance companies are registered and operating in Croatia. For the purpose of this work, the comparison of investments in the second and third pillars will be made using the parameters of returns and investment structure. According to the returns and investment structure, the B category of mandatory pension funds (OMFs) and open voluntary pension funds (ODMFs) are the most similar.