PURPOSE: To evaluate the hemodynamic change by portal tumor thrombus in hepatocellular carcinoma(HCC). MATERIALS AND METHODS: We reviewed 35 cases of combined spiral CTHA and CTAP in 25 HCC patients with portal tumorthrombus from April 1993 to October 1994, regarding to portal tumor thrombus, the involved area of arterioportal(AP) shunt and the development of cavernous transformation of portal vein, in comparison with hepaticand superior mesenteric arteriography. RESULTS: Spiral CTHA showed hyperattenuating tumor, portal tumor thrombus and hyperattenuating peritumoral parenchymal area. Spiral CTAP showed perfusion defect area including tumor, portal tumor thrombus and peritumoral area distal to portal vein obstruction. In 15 cases, portal tumor thrombus showed intraluminal and marginal hyperattenuating linear structures on CTHA due to transvasal AP shunt and tumor feeding arteries, which were corresponding to thread and streaks sign on hepatic arteriography. Cavernous transformation of portal vein was demonstrated in 15 cases as irregular periportal hyperattenuating collateral vessels on spiral CTAP. In 32 cases, portal vein was visualized on CTHA due to AP shunt. And according to shunt amount, we classified AP shunt into 4 grades. Grade I means only the presence of portal tumor thrombus without AP shunt, grade II with segmental AP shunt, grade III with one lobar AP shunt, and grade IV with both lobar AP shuntor the presence of cavernous transformation of portal vein. Grade I was seen in 3, grade II in 4, grade III in 13 and grade IV in 15 cases. CONCLUSION: Variable CTHA and CTAP findings were shown in HCC patients with portal tumor thrombus according to the amount of AP shunt and the presence of cavernous transformation of portal vein. Combined CTHA and CTAP are useful to differentiate the tumor thrombus from simple thrombus and are very sensitive method for detecting AP shunt. Understanding these findings related with portal tumor thrombus is important topredict patient}s prognosis and to decide treatment method.