'Age' is a major risk factor in cardiac surgery, however, the precise risks accompanying 'age' have not been fully analyzed. This study aimed to clarify the age-specific risks affecting the short-term outcome after isolated coronary artery bypass grafting (CABG). Data of 13488 procedures were obtained from the Japan Adult Cardiovascular Surgery Database, and the patients were divided into three groups; under 65 years of age ('Young', n=4420), 65-75 ('Middle', n=5485), and over 75 years of age ('Old', n=3583). As a preoperative profile, 'Old' tended to have extracardiac arteriopathy, left main stenosis, and emergency operation, whereas, 'Young' had more coronary risk factors (smoking, diabetes, dyslipidemia) and low left ventricular (LV) function. The 30-day operative mortality rate increased significantly with age ('Young': 1.7%, 'Middle': 2.3%, 'Old': 4.3%, P<0.0001). Renal dysfunction, arrhythmia, preoperative inotropes, and emergency surgery were the predictors for mortality common to all groups. Besides these, 'Young' only had cardiac factors as additional risks, whereas various factors including cardiac parameters, redo sternotomy, peripheral vascular disease, and chronic lung disease were the additional risks in the elderly. Thus, the elderly population was vulnerable to any kind of factors, and preoperative systemic evaluation was crucial in the elderly to help define the appropriate surgical candidates.