Hepatopulmonary syndrome (HPS), a complication of liver disease, is characterized by impaired gas exchange and results in increased morbidity and mortality. The role of angiogenesis in the pathogenesis of HPS will be studied by using a mouse model. Besides, a clinical multicenter study with Eurotransplant will be set up, focusing on HPS and portopulmonary hypertenstion in the setting of transplantation.