Although the relationship between deep venous thrombosis and pulmonary embolism is well known and studied extensively, the relationship between pulmonary vein thrombus (PVT) and systemic embolism such as cerebral infarction is unknown. 64-slice multidetector computed tomography (64-MDCT) scan can demonstrate PVT. We had reported two cases of small thrombus within the right upper pulmonary vein and the left upper pulmonary vein. A 74-year-old male with chronic atrial fibrillation was referred to be examined cardiac thrombus. 64-MDCT scan demonstrated large thrombi, which expanded from the right upper pulmonary vein to the left upper pulmonary vein and the left atrium. Three months warfarin therapy decreased the size of thrombi and changed the shape of thrombi. PVT is potentially life threatening condition and is thought to be a rare, but PVT seems to have been significantly underestimated. The 64-MDCT scan can assess PVT effectively and completely.