In this study, we will recruit asymptomatic patients with diabetes. At the time of enrollment, all patients will undergo two imaging studies (SPECT and CTA) within a few days apart. When patients had positive result in either study, they will undergo coronary angiography for confirmation. We will evaluate the results of two studies comparing with coronary angiography. When the patients are eligible for study, investigators will give information about the study and obtain written consent. The presence of chest pain symptom will be screened with Rose questionnaire. Medical history and physical examination will be performed, and baseline laboratory work-up will be performed. Investigators will evaluate the status of diabetic complication (retinopathy/nephropathy/cardiac autonomic neuropathy).