We encountered a case that was observed on coronary angiography (CAG) during coronary dissection after coronary angioplasty (PTCA) in which the dissected cavity disappeared on CAG but thrombolytic obstruction in the dissected cavity could be observed by intravascular echocardiography (IVUS). A 67-year-old woman was admitted with a diagnosis of acute myocardial infarction with ST elevation when experiencing chest pain. PTCR was performed for obstruction of the left circumflex artery (LCX) and the stenosis was improved to 90 percent. One month later PTCA was performed on an obstruction lesion in LCX and the feature of the dissected section at the same site was observed by CAG after PTCA. CAG showed that the dissected cavity had disappeared a year and a half later, but IVUS indicated thrombolytic obstruction in the dissected cavity.