The most common pulmonary complication of liver disease is the disruption of gas exchange, resulting in severe hypoxemia, a factor that alters the clinical course of patients with liver cirrhosis. One of these alterations is the hepatopulmonary syndrome, which is associated with a significant increase in morbidity and mortality, and is defined as a triad that includes liver disease, abnormal arterial oxygenation caused by demonstrable intrapulmonary vascular dilations, with consequent pulmonary shunt, and imbalance in diffusion and perfusion. An abnormal increase in pulmonary vascular resistance may also be found as a consequence of pulmonary arteriolar flow obstruction, resulting in clinical pulmonary hypertension called “portopulmonary hypertension”. This resembles primary pulmonary hypertension, with dyspnoea and fatigue, but without clinical or histopathological responses to therapies such as prostacyclin. These two pulmonary vascular conditions (hepatopulmonary syndrome and portopulmonary hypertension) in cirrhotic patients, or with portal hypertension, may coexist in the same patient, and hepatopulmonary syndrome usually develops before portopulmonary hypertension.Hepatopulmonary syndrome is thought to be mainly caused by two central processes: vasodilation and pulmonary angiogenesis, which are responsible for alterations in gas exchange, imbalance in ventilation-perfusion, and limitation of oxygen diffusion.This syndrome has currently become of special interest in the success of liver transplantation. Although it is rare, it is important to rapidly recognise its clinical expression in order to understand the pathogenesis involved in the patient with clinical, functional, and histological liver cirrhosis, given its progressive course and poor prognosis.