Backgrounds: Diabetes mellitus (DM) is associated with worse prognosis in patients with coronary artery disease, which is characterized by large amounts of necrotic core and calcium of the coronary plaque. We assessed the coronary plaque composition in patients with stable angina and DM according to the status of blood glucose. Methods: Study subjects consisted of 117 non-DM patients (mean 61.3 years old), 14 well controlled DM patients with HbA1c < 7.0% (mean 63.6 years old) and 37 poor controlled DM patients with HbA1c���7% (mean 61.7 years old) who underwent intravascular ultrasound-virtual histology (IVUS-VH) examination at the culprit lesion. Results: There were no significant differences among 3 groups in terms of age, gender, risk factors, imaged vessels and lipid levels, except for significant differences in fasting glucose levels (101짹14mg/dL, 124짹38mg/dL, and 153짹52mg/dL, respectively). Gray-scale IVUS showed that DM patients (n=51) had higher plaque volume (179짹91mm³ vs. 144짹92mm³, p=0.026) and longer lesion length (20.2짹7.8mm vs. 17.0짹7.3mm, p=0.013) than non-DM patient and plaque volume over the entire lesion was highest in poor controlled DM patients (144짹92mm³) compared with well controlled DM patients (152짹82mm³) and non-DM patients (189짹93mm³, p=0.038 compared with poor controlled DM patients). IVUS-VH findings showed that poor controlled DM patients had higher dense calcium (14.2짹11.2mm³ vs. 6.6짹3.1mm³, p=0.023 and 7.4짹8.2mm³, p<0.001) and higher necrotic core (14.2짹11.2mm³ vs. 6.6짹3.1mm³, p=0.029 and 7.4짹8.2mm³, p=0.001) than well controlled DM patients and non-DM patients, respectively, whereas fibrous and fibrofatty volume showed no significant differences among the groups. Conclusion: DM patients with well controlled blood glucose may have similar coronary plaque composition and plaque volume to non-DM patients, although lesion length was insignificantly longer than non-DM patients.