Purpose: 18F-flurodeoxyglucose (FDG) uptake on positron emission tomography (PET) scan has been found to reflect tumor aggressiveness and prognosis in various types of cancer. However, pattern of FDG uptake in biliary malignancies and its clinical significance have not been studied well. The purpose of this study was to assess the additional value of 18F-FDG PET in differential diagnosis and prognosis of cholangiocarcinoma (CC) according to the tumor location and tumor morphology. Materials and Methods: From April 2005 to May 2008, eighty two patients (M:F=55:27, age 66.2¡¾9.6 yrs) with CC underwent 18F-FDG PET. For semiquantitative analysis, the maximum standardized uptake value (SUVmax) was obtained from the primary tumor. The difference of SUVmax according to the tumor location and tumor growth pattern, such as scirrhous type, nodular type, polypoid type were compared. Results: Overall sensitivity of PET scan was 81.7% in CC. SUVmax on PET scan in intrahepatic CC was significantly higher compared to extrahepatic CC. In extrahepatic CC, polypoid type showed significantly higher SUVmax compared to scirrhous type. Conclusion: 18F-FDG PET may have a significant impact on clinical decision-making and on the management of Intrahepatic cholangiocarcinoma. And it is related to the shape of the tumor and the sensitivity of detection is higher in the mass-forming type than in the scirrhous type. (Nucl Med Mol Imaging 2009;43(4):317-322)