More recently, there has been as much development of the financial market as possible in the Republic of Croatia, so it is important that residents and potential future investors are familiar with all financial rules and financial instruments offered on the financial market. The subject of this final thesis are investment funds, where special attention will be directed to ETF funds. ETFs are an increasingly popular financial instrument for passive form of investment. There are a different number of ETF funds on the market, and their number has been growing over the years, which makes it possible to invest in different asset groups, in different sectors and geographic areas. To its investors, the market provides different types of funds that are open for investment, each of the funds has its own advantages and disadvantages that make it different and more suitable for the individual investor. The aim of this final paper is to elaborate in detail investment and ETF funds, from their historical beginnings, definitions, divisions, advantages and disadvantages and legal frameworks for the operation of investment funds.. The research conducted showed that it is well worth investing in investment and ETF funds, compared to the classic investment of money in the bank. When observing the impact of the COVID-19 crisis on investment funds, it was observed that there was a decrease in net assets in investment funds, the reason is that investors were withdrawing shares from the fund because they showed extreme sensitivity to the appearance of market volatility, which impairs liquidity and leads to the possibility of closing individual investment funds. While researching the movements of CROBEX10tr and SBI TOP fund, it is concluded that the CROBEX10tr fund achieved better turnover and that the fund price itself was lower, which shows the greater benefit of the fund compared to the Ljubljana SBI TOP fund.