Background: Hepatopulmonary syndrome (HPS), defined as hypoxemia and functional intrapulmonary right-to-left shunts in the presence of chronic liver disease, is a frequent complication of end-stage liver disease. The aim of this study was to determine the extent of pulmonary dysfunction and the prevalence of HPS in non-cirrhotic patients with chronic viral hepatitis. Methods: Lung function tests were carried out in 178 patients with chronic viral hepatitis (mean age 43.2 years, 95 smokers). To demonstrate intrapulmonary shunting, contrast echocardiography was performed in all patients with hypoxemia (paO(2)<70 mmHg) or a reduced diffusion capacity (DLCO<70% predicted). Results: The median results of lung function parameters (FVC, FEV(1), FEV(1)/FVC, TLC, DLCO, and blood gas analysis) were normal. Despite normal lung function, hypoxemia and/or DLCO reduction were observed in 17 of 178 patients (9.6%). A correlation with inflammatory activity, extent of fibrosis, or etiology was not found. Intrapulmonary shunting was observed in three of 17 patients. Two of these patients fulfilled the diagnostic criteria of HPS. Conclusions: Impaired gas exchange is a common finding even in non-cirrhotic patients with chronic viral hepatitis. HPS, however, was present in 1.1% of patients with chronic viral hepatitis and is thus not restricted to patients with liver cirrhosis, portal hypertension, or acute liver failure.