Approximately one third of the Finnish adult population are affected with overweight-related non-alcoholic fatty liver disease (NAFLD). NAFLD can appear as a simple fat accumulation in the liver of the liver, but in some individuals the condition may advance to non-alcoholic steatohepatitis (NASH) and even to liver cirrhosis. In many cases, NAFLD is detected as an incidental finding. In differential diagnosis, the most common alternatives are alcohol use, drugs and viral hepatites. For a patient with NAFLD, the risk factors of cardiovascular diseases should be investigated and the possibility of having NASH and liver fibrosis assessed. Targeted therapy for NASH is not yet available.