Ultrasonography, as screening method of choice, answers questions as to the size of the liver, the structure of the parenchyma, focal lesions and the dilatation of the biliary system. To characterize focal lesions, to stage tumors and for a better topographic localization, computed tomography or magnetic resonance imaging is useful. The differential diagnosis of focal lesions, such as cysts, hemangioma or focal nodular hyperplasia is achieved by the combination of laboratory, imaging and nuclear medicine methods. In other cases, needle-biopsy under sonographic or CT guidance is decisive.