Hepatopulmonary syndrome has yet not been sufficiently assessed in noncirrhotic portal hypertension. The prevalence of hepatopulmonary syndrome was determined in 31 consecutive patients with noncirrhotic portal hypertension (19 idiopathic portal hypertension, 7 portal vein thrombosis, 5 congenital hepatic fibrosis) and 46 patients with liver cirrhosis. Contrast echocardiography was carried out in all patients. Macroaggregated albumin lung perfusion scans were performed in patients with positive contrast echocardiogram. Hepatopulmonary syndrome was detected in 5 (10.8%) cirrhotic and 3 (9.7%) noncirrhotic portal hypertensive patients (2 idiopathic portal hypertension, 1 portal vein thrombosis). All patients with hepatopulmonary syndrome had an increased shunt fraction (13- 62%) and a decreased diffusion capacity of carbon monoxide (40- 79%), and 7 of them were hypoxemic (PaO2, 31.6- 69.8 mm Hg). These findings show that hepatopulmonary syndrome may occur in both liver cirrhosis and noncirrhotic portal hypertension and that portal hypertension is the predominant etiopathogenic factor related to hepatopulmonary syndrome.