Non-alcoholic fatty liver disease is the most common chronic disease of the liver in children. This term encompasses a wide spectrum of disorders of liver tissue: from mild steatosis to non-alcoholic steatohepatitis; the abnormalities may eventually lead to liver cirrhosis and the development of hepatocellular carcinoma. The prevalence of non-alcoholic fatty liver disease is estimated to be approximately 25% in the general population, while the rate for the paediatric population ranges from 7.6% to as many as 34.2% in obese children. In accordance with the current definition of non-alcoholic fatty liver disease, the condition is diagnosed after steatosis has been confirmed using histopathological or imaging methods and secondary causes of liver damage have been excluded, such as alcohol abuse, the use of hepatotoxic medicines and congenital or infectious diseases. The disease is most commonly diagnosed in the population of overweight and obese children; it often coexists with insulin resistance. There are reports of the impact of genetic factors on the development of the condition. Clinical signs and symptoms are non-specific: hepatomegaly, malaise and a sense of discomfort in the abdominal cavity. Basic diagnostic investigation includes aminotransferase test and abdominal ultrasound examination. Researchers pay much attention to non-invasive diagnostic methods such as serological markers and fibrosis scores. Due to the fact that no pharmacotherapy has a confirmed efficacy in the treatment of non-alcoholic fatty liver disease, the most important prevention and treatment methods in the paediatric population are lifestyle modification, physical activity and a balanced diet. The utility of vitamin E, ursodeoxycholic acid and metformin has not been confirmed by research. Due to the high prevalence of the condition and the risk of complications, familiarity with the problem is important particularly among general practitioners.