An oyster mushroom (Pleurotus ostreatus (Jacq.) P. Kumm) is a cultivated species of mushrooms characterizing with unique culinary and medicinal properties. Its’ nutritional value comes from proteins, carbohydrates, fatty acids, vitamins and mineral nutrients present in their fruitbodies. Because of a high content of fiber (mainly chitin) and low content of fat, they are a valuable element of an atherosclerosis diet. The fruitbodies of oyster mushrooms are an important source of biologically active substances, specific polysaccharides and polyphenols, which influence a human immune system, so that it fights against cancer cells. ß-D-glucans have an advantageous effect on digestive system, lower blood cholesterol and triglycerides level, decrease the risk of ischaemic heart disease. Active substances present in the mushrooms have antioxidant, antibacterial, antiviral, antidiabetic and anti-inflammatory properties. Numerous scientific studies prove high efficiency of the therapy with the use of preparations and extracts from Pleurotus ostreatus mycelia, both in prophylaxis and cure of civilization diseases, atherosclerosis and cancer.