CF is the genetic disease, causing the disorder of exocrine glands. The mucous secretions is abnormally viscid what generates infections of respiratory system, pancreatic insufficiency and the liver destruction caused by obliteration of intrahepatic bile ducts, in most cases. The second death cause is multifocal cirrhosis of the liver. The early detection of changes plays a basic role in a therapeutic approach, what is very important for prolongation of patients' live. The work presents the results of ultrasound examinations of 106 children aged: two months - 19 years with CF confirmed by genetic examinations, 8 with isolated lung form, 7 with isolated abdominal form and 91 with mixed form. The viral hepatitis B or C was excluded. The abnormalities of US picture of the liver were detected in every type of CF, in 79 cases. The most frequent was fibrous degeneration (38). The hyperechogenicity of the liver parenchyma (18), fatty degeneration (15) and mixed: fibrous and fatty changes (8) were observed as well. There was no portal hypertension in any case. The disturbances of flow in hepatic veins and/or hepatic artery were observed in 17 cases. The residual gall bladder was observed in 12 patients. The ultrasound is a very good (sometimes the only) method for estimation of hepatic and bile duct changes, even in infants, and is useful in establishing the indications for ursodeoxycholic acid therapy and for follow up. Work in progress.