Functional anatomy of the liver is based on three-dimensional arrangement of four liver systems – portal, arterial, biliary and the system of hepatic veins. On the basis of the intrahepatic course and branching pattern of the systems, the liver is divided into the left and right hemiliver, four sections or eight segments. Each liver unit has its own portal pedicle, composed of portal, arterial and biliary branch and is therefore functionally independent. The fourth liver system is the system of hepatic veins which run towards the inferior vena cava in other direction than the portal pedicle. The main hepatic veins follow the intersectional planes and provide venous drainage for the two adjacent sections. Knowledge of the liver functional anatomy, including liver division into segments and sections, is the basis for accurate localization of pathological process in the liver and safe surgical treatment and radiological intervention.