Cryptocurrency, as a type of digital money based on cryptography, was not primarily created as an investment asset. However, due to increasing media coverage and strong value growth, more and more investors, despite a less complete understanding of the cryptocurrency concept, decide to invest in cryptocurrencies in addition to traditional financial instruments. Given that traditional financial instruments do not provide satisfactory returns, the trend of increasing the value of cryptocurrencies is visible. Their growth is visible in the number of participants in that market. Many investors have started to invest their funds in these risky assets, especially in the Covid-19 pandemic. The idea of this paper was to analyze the relationship between cryptocurrencies and traditional financial instruments and to find out if investors can diversify their portfolios by investing in cryptocurrencies. Using the multivariate GARCH dynamic conditional correlation (DCC) and the multiple regression model, the following results were obtained: (i) due to high volatility during the analyzed period, the representative cryptocurrency Bitcoin achieves lower risk-adjusted return compared to S&P500; (ii) S&P500 has a statistically significant and positive effect on the price of Bitcoin. Therefore, our results suggest that Bitcoin cannot serve as a portfolio diversifier in turbulent times. Investing in cryptocurrencies involves a high level of risk resulting from insufficiently reliable information, and is more of a speculation than an investment.