Purpose: The paper aims to identify the monitoring effect by financial investors and their potential role to mitigate agency costs resulting from concentrated and dispersed ownership. Design/Methodology/Approach: Using the sample of 440 companies from the Warsaw Stock Exchange listed in 2010-2014, we examine whether financial investors may mitigate the agency problems of dispersed and concentrated ownership. Findings: We observe that ownership by financial investors is positively correlated with company value. Adding to the debate on the monitoring role of financial investors, we note that investments by control-oriented institutions and portfolio-oriented investors are correlated with higher Tobin’s Q. Practical implications: The results indicate the positive effect of the monitoring by financial investors, which can offset some limitations of insufficient investor protection in emerging markets. Originality: The study is based on a unique sample of companies listed on the Warsaw Stock Exchange, distinguishing between control-oriented and portfolio-oriented financial investors.