A 68-year-old man was admitted with intermittent chest tightness. Coronary angiography revealed subtotal occlusion of right coronary artery (RCA). After successful stenting from middle to proximal RCA with two Cypher stents, angiography showed a "Rolling filling defect" at distal aneurysmal dilatation of RCA. Intravascular ultrasound (IVUS) confirmed the "Rolling filling defect" as a trapped air bubble just in RCA distal aneurysm. By using a 2.5 x 20 mm balloon anchoring at distal RCA, a 5Fr. ST01 catheter was advanced into distal RCA and aspirated the "Rolling filling defect" successfully. The case highlights the importance of preventing iatrogenic trapped air bubble in usual daily practice. Once it happens, several devices may utilize for aspiration including "5 in 6" aspiration technique or thrombo-suction catheters. Furthermore, IVUS can help for differential diagnosis in such scenario.