Pulmonary arterial hypertension (PAH) and cor pulmonale were found in a patient with paroxysmal nocturnal hemoglobinuria (PNH). Autopsy revealed widespread thromboses in pulmonary microvasculature. Vascular thromboses attributed to hypercoagulability have been found in PNH in many organs, including the lungs. PAH has not been reported, however. This disease should then be considered a rare cause of PAH.