Purpose : To prove whether the arterioportal shunt, especially transvasal shunt is one of the cause of the hypovascular hepatocellular carcinoma. Materials and Methods : We evaluated the early phase images of table incremental dynamic CT and hepatic angiography in 20 cases of hepatocellular carcinomas with transvasal arterioportal shunt. Results : In hepatic arteriography, 18 cases were hypovascular and the remained 2 cases showed hypervascular tumor staining than surronding normal hepatic parenchyme. In the early phase dynamic CT, 18cases were hypodense(including 4 cases of focal hyperdensity in hypodense background), one was isodense and remaining one was hyperdense. Conclusion : Arterioportal shunt, especially transvasal shunt may make originally hypervasular hepatocellular carcinoma to hypovascular lesion in the early phase dynamic CT or hepatic arteriography. In attempt to differentiate hepatic masses by tumor vascularity in recently widely used table incremental dynamic CT, the vascular pattterns of the mass should be considered by close evaluation of vascular pattern of the liver, such as morphology of perfusion abnormality and arterioportal shunt, etc.