Due to their low caloric value and the fact that they don't contain cholesterol, mushrooms are gaining in popularity in the human diet. Because of their high protein content they are used as a meat substitute in the diet of vegetarians and vegans. They contain various nutrients such as fiber and vitamins, primarily B vitamins, and some mushrooms also contain vitamin D. Due to their ability to absorb substances from the soil, mushrooms are a good source of minerals, especially potassium. In addition to their nutritional value, some mushrooms contain polysaccharides, steroids, triterpenes and other ingredients that give them medical properties. Some mushrooms contain antibiotics, substances effective against tumors and viruses, substances that lower cholesterol, prevent blockage of blood vessels, regulate blood pressure, improve blood circulation in a harmless way, improve important vital functions and strengthen the immune system. The aim of this paper is to describe, through selected representatives, the bioactive mechanisms of action of fungi that are used or have the potential to be used for medicinal purposes. The mushrooms included in this paper are: Lentinula edodes, Grifola frondosa, Hericium ernaceus, Ganoderma luidium, Medusomyces gisevii Inonotus obliquus and Kefir mushroom.