Abstract
The article attempts to explain the essence of excluding unlawfulness of an act in administrative law. First, the concept of unlawfulness of an act has been analysed and arguments for its formal and material recognition have been presented. According to this approach, an unlawful act is an illegal act that is harmful, i.e. interferes with the good (public interest) protected by law. Exclusion of unlawfulness consists in statutory indication of the extent of illegal acts that are not harmful. The article also provides a legal dogmatic verification of the hypothesis according to which Polish substantive administrative law regulates the circumstances excluding unlawfulness of an act.