The hepatopulmonary syndrome (HPS) is a rare complication of liver cirrhosis and is characterised by the typical triad of liver cirrhosis, arterial hypoxemia, and intrapulmonary vascular dilatation. Except for pleural effusions associated with liver cirrhosis no other disease of the lungs or the heart is detectable. The structural hallmark of HPS is dilatation of pulmonary precapillary vessels which impairs diffusion-perfusion and causes unequal ventilation-perfusion. The diagnosis of HPS is based on PaO2 measurements when breathing room air and 100% oxygen. The increased intrapulmonary vascular diameter allows microbubbles to traverse the lung capillaries when agitated saline is administered intravenously. Only on rare occasions is a patient limited by his pulmonary impairment, the leading morbidity is that of liver disease and its classical complications. Drug therapy is of no proven benefit, oxygen supplementation might improve dyspnea. Vascular embolisation of discrete arteriovenous shunts, if present, or liver transplantation may dramatically improve pulmonary function in selected patients.