It is important to diagnose hepatocellular carcinoma (HCC) correctly and in early stage, because viral hepatitis and liver cirrhosis are often complicated by HCC. Noncontrast and enhanced CT and MRI are very useful to visualize and diagnose HCC objectively. Especially, CT and MR imaging with dynamic study is essential to diagnose HCC, because it is usually hypervascular. Dynamic CT and MR study also improve differential diagnosis in the characterization of the tumor. However, to perform useful dynamic study, it is necessary to use a CT unit which can make a helical scan, or a MR system with fast imaging technique available that can obtain more than 15 slices within a single breath hold. Tissue specific contrast medium, such as superparamagnetic iron oxide that is available only on MRI, is also useful for diagnosis of HCC.