The article deals with the unequal treatment of company shareholders. The analysis is conducted from the perspective of minority shareholders and their interests. The author uses a research method that presents the position of minority shareholders in companies on the basis of the agency theory. Szewc-Rogalska shows the influence of dominant shareholders and top managers on the market value of companies (in light of both Polish and foreign empirical studies), along with a review of ways to limit inequality among shareholders. The analysis reveals that the position of minority shareholders can be threatened by agency conflicts that occur in companies. In companies with concentrated ownership, these conflicts are different than in companies with scattered ownership. After a dominant shareholder exceeds a certain level of ownership, the company is likely to face problems resulting from the shareholder’s desire to pursue their own interests at the expense of other shareholders. Inequalities among shareholders cannot be eradicated completely, and there is no single fully efficient mechanism to protect minority shareholder rights. A diverse range of activities is needed, including improved information transparency of companies and better corporate supervision, in addition to increased activity of minority shareholders and the creation of legal mechanisms to protect their interests.