The effect of diabetes mellitus (DM) on angiographic restenosis and clinical outcomes after implantation of drug-eluting stents (DESs) has not been investigated in real-world practice. This study consisted of 226 patients who had DM and 560 patients who did not who underwent DES implantation between February 2003 and December 2003. We retrospectively compared the incidence of 6-month angiographic restenosis and 9-month major adverse cardiac events (MACEs), defined as cardiac death, myocardial infarction, and target lesion revascularization, between patients with and without DM. The 6-month angiographic restenotic rate (10.1% vs 8.2%, p = 0.41) and late loss (0.41 +/- 0.63 vs 0.36 +/- 0.65, p = 0.31) were similar between patients with and without DM. In addition, incidences of MACEs (4.9% vs 4.8%, p = 1.00) and target lesion revascularization (4.4% vs 4.1%, p = 0.84) were similar. Patients who had insulin-dependent DM manifested higher prevalences of restenosis (25.0% vs 8.5%, p = 0.04) and MACEs (17.2% vs 3.1%, p = 0.01) compared with patients who had non-insulin-dependent DM. In conclusion, in this study of real-world patients who underwent DES implantation, patients who had DM had restenotic rates and clinical outcomes that were similar to those in patients who did not have DM.