Cryptocurrencies are a burning topic in modern times of investment strategies. Since the cryptocurrency market is classified as emerging market, this paper compiles a portfolio of emerging markets from the indexes of four EU countries and one cryptocurrency. The aim was to investigate how the incorporation of Bitcoin cryptocurrency into the portfolio affects the performance of the portfolios of these countries, and by drawing an effective boundary to identify where Bitcoin is relative to other indekses in the portfolio. Initially, the tory assumptions of the method by which empirical analysis was later made were outlined. It also explained the meaning of emerging market terms and presented formulas for calculating EU countries' indexes. The countries whose indexes were used in the analysis are: Croatia, Hungary, Romania and Poland. The method used to draw an effective boundary is Markowitz's modern portfolio theory. Applying this method at the efficient frontier created a portfolio of minimum variance for the portfolio with and without cryptocurrency. Although Markowitz's theory has some drawbacks, the empirical analysis concludes that Bitcoin increases portfolio efficiency in emerging markets of selected EU countries, where the expected risks or standard deviations of a portfolio that includes cryptocurrency are even smaller with higher returns than portfolio that does not consist of cryptocurrency. Notwithstanding the increased efficiency of the entire portfolio, the weightings of the minimum variance portfolio remained unchanged. Given that cryptocurrency prices are characterized by high volatility, investing in such a portfolio will depend on investors' aversion to risk. In the analysis conducted, Bitcoin is on the efficient frontier, and all instruments on the efficient frontier are, according to modern portfolio theory, efficient, so it can be said that such investments are very challenging. Also, the empirical analysis compared the portfolio of these countries during the crisis and after the crisis. The graph shows that the situation in these countries began to improve rapidly after the crisis, while during the crisis the returns were negative, which means that there was no room for investment in such markets.