Sixty seven cases of segmental arterial hyperperfusion and thirty one eases of segemental portal hypoprfusion detected among 803 cases of arterial and portal dominant CT were studied for the evaluation of etiology and mechanism causing intrahepatic segmental abnormal perfusion in normal portion of the liver around hepatic mass. Hepatic masses causing segmental abnormal perfusion were hepatocellular carcinoma, peripheral cholangiocarcinoma, metastasis, abscess, and cavernous hemangioma. Segmental portal hypoperfusion was seen on the area of segmental arterial hyperperfusion in all the cases a nd segmental arterial hyperperfusion was seen on the area of segmental portal hypoperfusion in 77% of cases. In conclusion. there are intrahepatic segmental portal and arterial abnormal perfusions in normal portion around hepatic mass, and these phenomena may be developed with close reciprocal alteration between both portal and hepatic arterial flows.