PURPOSE: To describe the CT findings of portal vein aneurysm in eight patients. MATERIALS AND METHODS: Allpatients included in this study (two men and six women) under went CT examinations between October 1996 and June1998. Of these eight, three were suffering from hepatic disease and portal hypertension. We determined thelocation, shape, size, and characteristics of the lesions, and the presence or ab-sence of portal vein anomaly. RESULTS: S even patients had intrahepatic portal vein aneurysm (at the umbilical por-tion of the left portal veinin five patients, between the transverse and umbilical por-tion of the left portal vein in one, and at thebifurcation of the anterior and posterior branch of the right portal vein in one), while extrahepatic portal veinaneurysm, at the confluence of the superior mesenteric and splenic vein was found in only one. Lesions werecyst-shaped in seven cases and saccular in one, and showed well - circum scribed, markedly enhanced mass, whichcommunicated with the portal vein and/or gives off major branches. Portal vein anomaly, in which the rightanterior segmental portal vein originated from the umbilical portion of the left portal vein, was seen in threepatients. In all three, intrahepatic portal vein aneurysm was present at the umbilical portion of the left portalvein, and in one, the umbilical portion of the left portal vein was located to the right of the Cantlie line. CONCLUSION: CT examination can help reveal portal vein aneurysm by detectinga well - circumscribed, markedlyenhanced mass which communicates with the portal vein and/or gives off major branches.