The authors report a case of idiopathic portal hypertension in which radioaccumulation in the peripheral region of the liver decreased markedly. On dynamic CT, peripheral regional enhancement of the liver was seen in the arterial phase. The region was hypointense on T1-weighted MR images and hyperintense on T2-weighted images. On portograms via the superior mesenteric artery, markedly decreased portal venous perfusion was seen in the peripheral region of the liver. Tc-99m galactosyl human serum albumin (GSA) liver scintigrams showed decreased accumulation in the peripheral region and unchanged accumulation in the central region of the liver. Tc-99m GSA liver scintigraphy clearly showed localized liver dysfunction in the peripheral region.