Sixteen portal cavernomas were examined with dynamic computed tomography (CT) and confirmed by sonography. Characteristic features included loss of the normal vascular structure and the presence of sinuous collateral pathways which were enhanced during the portal phase. Fifteen patients exhibited transient differences in hepatic attenuation and peripheral arterial concentration of contrast material. Increased arterial flow in the poorly perfused territories is suggested as a cause of these hemokinetic abnormalities.