A 54-year-old Japanese woman with primary biliary cirrhosis (PBC) was admitted to our hospital due to hepatic coma and refractory pleural effusion. The physical examination revealed clubbed fingers and collateral veins. The patient had an increased alveolar-arterial oxygen gas tension difference. The levels of anti-mitochondrial antibody (AMA) and AMA M2 was 80 times normal. A technetium 99m-labeled macro-aggregated human albumin scintigram showed uptake in the spleen and the kidneys. A diagnosis of hepatopulmonary syndrome (HPS) was made. HPS may be overlooked because of the lack of symptoms. We conclude that closer attention should be paid to the occurrence of HPS.