During the past years, development of financial markets led to development of financial instruments and their accounting treatmnent. Developing accounting standards provide us more reliable monitoring od financial instruments. The subject of this paper is International Accounting Standard 39: Financial instruments – Recognition and Measurement and its application in subsequent measurement of financial instruments. Main goal of this thesis is to emphasize the importance od financial instruments (financial assets and liabilities) clasification for their subsequent measurement, and the importance of fair value concept for subsequent measurement. The influence of subsequent measurement of financial instruments on financial position and profitability is explainded trough the example of investment fund. We can conclude that subsequent measurement can have a significant impact on financial position and profitability, especialy when it comes to investment funds, since they usually have a large share of financial instruments within their assets.