The article seeks to establish whether and why family firms listed on the Warsaw Stock Exchange (WSE) are more likely to avoid paying taxes than other companies. The author examines the tax avoidance practices of listed firms, using a long-run measure of tax avoidance drawn from the literature: the so-called three-year cash effective tax rate (“cash tax paid divided by pre-tax book income”). The author demonstrates that family firms exhibit greater tax avoidance than their non-family counterparts, as shown by their lower cash effective tax rate. The difference in the effective tax rate between family and non-family firms is more than 4.0%, the author says. The research validates the hypothesis that family firms are ready to seek tax savings even at the expense of potential fines imposed by tax inspectors and reputation damage. The author also finds that diversified family firms and family firms that do not depend on external finance exhibit greater tax avoidance. Among family firms, a higher level of tax avoidance is characteristic of “opaque” firms and firms using dual-class shares, Kałdoński says. This indicates that diversification and financial independence tend to lower the costs of tax avoidance, while a lack of transparency and dual-class shares can be used for tax avoidance purposes, the author adds.