BACKGROUND: Diabetes has been regarded as a major predictor of restenosis after percutaneous coronary intervention (PCI) with bare-metal stents. With the introduction of DESs, the angiographic rates of restenosis at later months have reduced dramatically but less prominently in diabetic patients. We sought to identify parameters influencing the likelihood of restenosis after drug-eluting stent (DES) implantation in diabetic patients. METHODS: Stented patients (n=840) with DESs were retrospectively reviewed for inclusion in the study from the PCI database. From this database, 211 (25.1%) out of 840 patients with six-month angiographic follow-up had diabetes. Predictors of coronary restenosis were identified with univariate and multivariate logistic regression analyses. RESULTS: Restenosis (> 50% of the luminal diameter stenosis during the six-month follow-up) occurred in 92 of 629 (14.6%) nondiabetic and 44 (20.9%) of 211 diabetic patients (p <0.001). Multivariate parameters for predicting restenosis in the diabetic group were current smoking [Odds Ratios (OR) = 1.923, 95% Confidence Interval (CI) 1.055 to 4.725, p=0.036], higher C-reactive protein (CRP) (OR=1.031, 95% CI 1.011 to 1.075, p=0.043), smaller reference diameter (RD) before DES implantation (OR=0.501, 95% CI 0.110 to 0.965, p=0.040), and smaller RD (OR=0.455, 95% CI 0.120 to 0.814, p=0.026) after DES implantation. For every millimeter of increase in the post-PCI minimum lumen diameter (MLD), there was an OR of 0.447 (95% CI 0.068-0.876) for restenosis. For every millimeter of increase in the stent length, there was an OR of 1.065 (95% CI 1.021-1.119) for restenosis. CONCLUSIONS: Even with the introduction of DES, diabetes remains a significant predictor of coronary restenosis especially in cases of small baseline and post PCI vessel size, longer stent length, current smokers, and high level of CRP.