We performed this study to evaluated detectability and delineation of extent of hepatocelluar carcinoma be comparison between nonenhanced and contrast-enhanced CT scan During a three-year period 174 patients with hepatocellular carcinomas were examined by CT at Seoul National university Hospital. Fifty-there patients had histological proof by operation or liver biospy while 121 patients were diagnosed by characteristic angiographic finding and elevated a fetoprotein level (>500ng/ml). All 174 patients were studied was a CT-9800 scanner. CT scans wee obtained both before and after ad-ministration of contrast medium. Contrast material was given by bolus injection of 120ml of ioxitalamate meglumine. CT findings were divided into three categories; Good : tumor is noted and extent of tumor is clear-ly defined; Fair : tumor is noted but extent of tumor is not defined; Poor : tumor is not noted. In 165 cases of the tumor on nonenhanced CT scans 131 cases (79%) showed low-density 29 cases (18%) iso-density one case high-density and 4 cases (2.4%) mixed density. In 174 cases of the tumor on contrast-enhanced CT scans 170 cass(97%) showed low-density 3 cases (1.8%) iso-density and 1 cases mixed density (0.6%) in 165 cases of that tumor on nonenhanced CT scans 64 cases (39%) were categorized as good in tumor on contrast-enhanced CT scans Our sesults indicate that contrast-enhanced Ct scans are better than nonenhanced CT scans in detecting the tumor and defining them and reduce radiation exposure to the patients by nonenhanced CT scans in clinically suspected hepatocellular carcinoma.