PURPOSE: To elucidate the dynamic features of CT scans in peripheral cholangiocarcinoma for the differentiation of this tumor from various primary hepatic neoplasms. MATERIALS AND METHODS: Materials were 24 cases of pathologically confirmed peripheral cholangiocarcinoma. Contrast enhancement patterns of central and peripheral portion of the masses were analyzed at three phases including arterial dominant(22), tissue equilibrial(24), and postequilibrial(9). Other associated CT findings and laboratory data were analyzed. RESULTS: Serum total billrubin was mostly below 2mg/dl(22/24), hepatitis B surface antigen was positive in 0nly 9%, serum alphafetoprotein was elevated in 18%, carcinoembryonic antigen in 47%, cancer antigen 19-9 in 60%. In the arterial dominant image(22), 50% of the cases showed peripheral hyperdensity and 50% total hypodensity. In the tissue equilibrial images(24), 63% showed total hypodensity, 25% peripheral hyperdensity, and 13% total isodensity. In the postequilibrial images(9), 45% showed peripheral hypodensity, 33% total hyperdensity, and 22% total hypodensity. The relative CT density of central portion of mass was higher in later phase than earlier phase. Associated findings were IHD dilatation(18) or stone(2), lymphadenopathy(11), ipsilateral lebar shrinkage(7), surrounding cystic mass(2), calcification within the mass(2) and choledochal cyst (2). CONCLUSION: Dynamic features of CT scans were useful for the systematic differentiation of the peripheral cholangiocarcinoma from various primary hepatic neoplasm.