Mushrooms have been an important part of the human diet for thousands of years. In many cultures, they are not only a source of food but also a raw material with medicinal potential. Their unique structure and chemical composition make them an interesting subject of research in the fields of nutrition, food technology, and medicine. Currently, there is a growing interest in mushrooms as functional foods that can contribute to health improvement and support the body in fighting diseases. A possible hazard linked to eating tree-growing fungi is the accumulation of heavy metals in their fruiting bodies, as these organisms have a strong ability to bioaccumulate such elements. For this reason, it is essential to avoid collecting fungi from polluted areas and to respect recommended safety limits for single servings. Despite certain restrictions—especially concerning vulnerable groups such as children—fungi can still be considered a functional food with health-promoting properties. While in vitro studies on tree fungi have revealed a rich diversity of biologically active metabolites, translation of these findings to in vivo or clinical efficacy remains limited to a few well-studied examples. The aim of this study was to assess the current state of knowledge on the chemical composition and biological potential of selected Polish species of wood-inhabiting mushrooms (Laetiporus sulphureus, Pleurotus pulmonarius, Pseudohydnum gelatinosum, Sparassis crispa, Armillaria, and Tricholomopsis rutilans in the context of their nutritional and therapeutic applications.