We evaluated the sensitivity and specificity of a diagnosis of peripheral arterial occlusive disease (PAOD) as a predictor of the severity of coronary artery disease (CAD) in patients with and without diabetes. A total of 302 patients were assigned to groups according to the angiographic severity of their CAD and their diabetes status. Both PAOD and severe PAOD were diagnosed by measuring the ankle-brachial index (ABI) and toe-brachial index (TBI). A diagnosis of PAOD had a low sensitivity (34.3%) but a high specificity (87.0%) for detecting patients with severe CAD. Sensitivity was higher in patients with diabetes (52.4%) than without (19.5%), whereas specificity was higher in patients without diabetes (95.4%) than those with diabetes (69.8%). A diagnosis of severe PAOD had a higher specificity (96.0%), but a very low sensitivity (16.4%). We conclude that a diagnosis of PAOD among patients with CAD had a low sensitivity but a high specificity for detecting those with severe CAD, particularly in patients without diabetes.