We compared the computed tomographic (CT) and angiographic presentations of hepatocellular carcinoma (HCC) with or without cirrhosis in the United States and Japan. Tumors in the United States were advanced and less frequently associated with liver cirrhosis (association of cirrhosis: United States 56.2%, Japan 91.0%. In patients with cirrhosis, the size of the tumor tended to be smaller, and nodular tumors (single or multiple) were frequent. In early stage of HCCs with cirrhosis, tumors were hypovascular without a capsule. In advanced stage, tumors were hypervascular and a capsule was frequently observed around the tumor both with CT and angiography. HCCs without cirrhosis were seen in younger patients. These tumors were large at the time of diagnosis. A massive or diffuse mass without a capsule was frequently seen. Most tumors were hypodense on precontrast CT and hypervascular on angiography. Lymph node enlargement was significantly frequent. The radiological characteristics of HCC in both countries were significantly different depending upon associated cirrhosis, as well as the time of the diagnosis.