Two previously healthy patients were admitted for chest pain, haemoptysis and dyspnoea. Perfusion-ventilation lung scanning demonstrated pulmonary embolism. Lower extremity duplex imaging and contrast venography revealed a thrombosed popliteal vein aneurysm as the source of emboli. After immediate anticoagulant therapy, the thrombo-embolic source was excluded by aneurysmectomy with lateral venography in the first patient. The second patient was treated by anticoagulants and percutaneous vena cava inferior filter placement to prevent recurrent pulmonary embolism. Anatomopathological findings, possible origin, diagnostic modalities and medical and surgical treatment of popliteal vein aneurysm are discussed.