Klippel-Trenaunay syndrome (KTS) is a congenital disorder characterized by venous malformations and a predisposition to pulmonary embolism. We reviewed the imaging findings of 7 adult patients with KTS who underwent thoracic CT. While the superficial manifestations of KTS predominantly affect the extremities, patients frequently develop abnormalities of the pulmonary arterial system, particularly chronic thromboembolic pulmonary hypertension. Additionally, some patients are seen to develop pulmonary arteriolar aneurysms; the physiologic significance of this finding is unknown at this time. Radiologists should be aware of these potential findings and have a high index of suspicion for chronic PE in patients with KTS.