Coronary angiography revealed three-vessel disease in a 56-year-old male with two previous myocardial infarctions. Coronary bypass surgery was initially ruled out by cardiac surgeon because of the poor left ventricular function (EF: 23%), despite moderate viability signs during conventional isotope techniques. Positron emission tomography with 18FDG indicated a large periinfarction area of hibernating myocardium. Accordingly, coronary bypass grafting was performed. Postoperatively, the symptoms disappeared, the left ventricular wall motion abnormalities (with the exception of the scarred region demonstrated by PET) improved, and the global left ventricular function increased significantly. This case and the role of cardiac PET study for prediction of the result of revascularization are discussed.