A case of acute aortic dissection complicating acute inferior myocardial infarction diagnosed by accidentally inserting the catheters into the false lumen during the emergency cardiac catheterization is reported. Although the incidence of acute aortic dissection developing acute myocardial infarction is not very rare, an aortogram and coronary angiogram via the false lumen has never been seen before. This case also illustrates how myocardial infarction can mask aortic dissection. Cardiologists should pay more attention to this severe complication of acute aortic dissection and perform transthoracic echocardiography prior to catheterization or fibrinolysis.