Background: Diabetes mellitus (DM) has been known as an independent risk factor for in-stent restenosis and adverse clinical outcomes. The aim of the study was to compare vascular responses of sirolimus-eluting (SES), paclitaxel-eluting (PES), and zotarolimus-eluting stent (ZES) between the patient with and without DM using optical coherence tomography (OCT). Methods: Total 182 lesions (62 lesions in 59 diabetic patients and 120 lesions in 117 non-diabetic patients) undergoing follow-up coronary angiography at 9 months after implantation of 80 SES, 50 PES, and 52 ZES were enrolled. We performed OCT to evaluate the degree of neointimal hyperplasia (NIH) inside each strut and stent apposition. Results: 42,347 struts in 4,716.8-mm single-stented segments in total were analyzed. The baseline clinical characteristics between DM and non-DM group are comparable. There were no significant differences in mean NIH thickness (169.4짹 128.9關m in DM vs. 176.1 짹 122.6關m in non-DM, p = 0.671) and percentage of malapposed struts (1.43 짹 4.68% in DM vs. 0.75 짹 2.58% in non-DM, p = 0.125). In the subgroup analysis of patients with SES (30 DM vs. 50 non-DM), the frequency of microthrombi [15 (51.7%) vs. 10 (20.0%), p = 0.003] and percentage of malapposed struts (2.8 짹 6.5% vs. 0.7 짹 1.4%, p = 0.037) were significantly higher in DM group than in non-DM group. Conclusions: At 9 months after stent implantation, there were no significant differences in neointimal coverage between DM and non-DM patients. In addition, much higher rate of microthrombi and malapposition for DM patient with SES were observed.