Background and Objectives: Advanced glycation end-products (AGEs) are known to contribute to the development of atherosclerosis by receptor or non-receptor medicated mechanisms. We investigated whether serum levels of AGEs are related to the presence or severity of coronary artery disease (CAD), and also explored the association between serum levels of AGEs and arterial stiffness according to diabetes status in patients suspected of having CAD. Subjects and Methods: The measurement of serum AGEs and arterial stiffness using brachial-ankle pulse wave velocity (baPWV) were performed in 145 consecutive patients (63짹9 years, 58% men) who received coronary angiogram for evaluation of CAD. Results: Forty-four diabetic and 101 non-diabetic individuals were classified into 3 subgroups based on the number of diseased vessels with obstructive CAD: 0-, 1-, and 2 or more vessel diseases (VDs). Serum AGEs were significantly higher in diabetic patients with obstructive CAD than in those without obstructive CAD (2.16짹0.29 vs.1.85짹0.29mU/ml, P=0.010) and were significantly correlated with the number of VDs only in diabetes (r=0.504, P<0.001). Serum AGEs were significantly correlated with baPWV in neither diabetes nor non-diabetes patients. In the receiver operating characteristics analysis to determine the optimal cut-off value of serum AGEs as a predictor of obstructive CAD in diabetics, the cut-off value of 1.98 mU/ml had 64% sensitivity and 63% specificity. In multiple regression analysis, serum AGEs independently predicted obstructive CAD and were associated with the number of VDs in diabetic individuals. Conclusions: Serum AGEs independently predict obstructive CAD and the severity of coronary atherosclerosis irrespective of arterial stiffness only in diabetic patients with suspected of having CAD. Evaluation of PWV and serum AGEs together may be more effective to identify the risk of CAD in diabetic patients.