Objective:To analyze the association of type 2 diabetes mellitus (DM) with the clinical and coronary angiographic features of coronary heart disease (CHD) in patients aged over 70 years old. Methods: A total of 310 elderly patients with coronary angiographconfirmed coronary diseases, who were treated in Changhai Hospital during Apr. 2006 to Jul. 2008, were retrospectively analyzed. The patients were further divided into 2 subgroups according to the presence of DM: DMCHD group (n=155) and nonDMCHD group (n=155). The age, gender, blood pressure, blood lipid, ejection fraction (EF), the angiographic outcomes, etc. were analyzed and compared between the two groups.Results: The incidence of hypertension was significantly higher in the DMCHD group than in the nonDMCHD group (P<0.05). The fasting blood glucose (FBG), triglyceride (TG), low density lipoprotein cholesterol (LDLC), and fibrinogen (FIB) were significantly higher than those in the other group (P<0.01), and the high density lipoprotein cholesterol(HDLC) was lower than that in the other group (P<0.05).The EF value in the DMCHD group was significantly lower than that in the nonDMCHD group (P<0.01). Among the 35 (22%) patients preliminarily diagnosed as having DM, 14 (40%) would be misdiagnosed if the diagnosis depends solely on FBG without oral glucose tolerance test (OGTT). The prevalence of diffusive coronary lesions in the DMCHD group was significantly higher than that in the nonDM group (P<0.01). DMCHD group also had significantly higher coronary stenosis index (P<0.01) and more occlusive vessels than nonDMCHD group. Conclusion: The missed diagnosis rate of DM is high in CHD patients. Compared with nonDMCHD patients, DMCHD patients are at higher risks for coronary disease and have more severe coronary lesions.