Non-alcoholic fatty liver disease (NAFLD) is a common chronic disease, uniting clinical and pathological changes in a liver: steatosis, non-alcoholic steatohepatitis, fibrosis and cirrhosis. NAFLD is associated with obesity especially of abdominal type and metabolic syndrome, that raises cardiometabolic risk and effects morbidity, prognosis of the disease and life expectancy of patients. This article describes the basic mechanisms of development of NAFLD, classification, prognosis of the disease, diagnosis and treatment.