Cystic adventitial disease of the popliteal artery is a rare cause of lower extremity occlusive disease. We report 2 cases of this disease. Two male patients aged 27 and 59 year old complaining of intermittent claudication visited our vascular service. Angiography showed a smooth sharp defect of the popliteal artery. Postcontrast computed tomography (CT) scanning and magnetic resonance image (MRI) showed a cystic lesion around the popliteal artery. One patient underwent resection of the cyst, which in the other patient endscopic surgery was performed with the aid of intravascular ultrasonograpy and intravascular endscope. Fifty three cases of this disease have been reported in Japan so far. These patients included 45 men and 8 women with a mean age of 47.7, ranging from 19 to 76 years old. Chief complaints were commonly intermittent claudication and sensory disturbance. In all cases, angiography revealed a smooth sharp defect. Recently 3D-CT scan, ultrasonography and magnetic resonance angiography (MRA) also are accurate for cystic lesions around the popliteal artery and these new technologies easily distinguish such cases from arteriosclerosis obliterans, Buerger disease and popliteal entrapment syndrome. Treatment consist resection of the cyst, in 27 cases reconstruction of the popliteal artery using a saphenous vein graft or artificial graft in 19 cases, percutaneus aspiration under the guide of CT and endscopy in 2 cases and 1 with spontaneous resolution, was seen in 1 case. In conclusion, we encountered 2 cases of cystic adventitial disease of the popliteal artery. 3D-CT scan, ultrasonography and MRA were useful for preoperative diagnosis and evaluation of postoperative condition.