Hepatopulmonary syndrome is essentially the triad of liver disease, pulmonary vascular dilations and abnormal arterial oxygenation, which can result in severe hypoxia. We managed two cases of 9 and 49-year-old males for liver transplantation with hepatopulmonary syndrome. Preoperative evaluation showed decreased diffusion capacity of carbon monooxide and severe hypoxemia, while breathing room air (PaO2 < 60 mmHg) but they responded to oxygen therapy. The pulmonary vascular resistance was low, consistent with an intrapulmonary vascular shunt but the pulmonary artery pressure was normal, reflecting a high cardiac output. Intraoperative oxygenation was satisfactory (PaO2 of 100 - 200 mmHg) in spite of a high shunt fraction (Qs/Qt 18.5 +/- 9.2%). This means that the impairment in gas exchange is not the result of a true shunt, suggesting the presence of a functional shunt, which is characterized by diffusion-perfusion impairment. The intraoperative course was uneventful in the two patients and they are in a successful postoperative course. In case 1, the hypoxemia was resolved promptly, but in case 2, it was persistent for sixteen months after transplantation. The hypoxemia itself in hepatopulmonary syndrome is not regarded as a contraindication to liver transplantation. (Korean J Anesthesiol 2001; 40: 677 ~ 683)