Backgrounds: Recently drug-eluting stent (DES) has been used for the treatment of patients with ST segment elevation myocardial infarction (STEMI), the long-term benefits of DES during primary percutaneous coronary intervention (PCI) in diabetic patients which have high risk of adverse outcomes remains uncertain. The aim of this study is to evaluate the safety and efficacy of DES implantation in primary PCI with or without diabetes. Methods: Three hundred ninety seven patients (414 lesions) were consecutively included from August 2005 to July 2007. All patients were divided to 2 groups: diabetes or non-diabetes. Major adverse cardiac events (MACE: cardiac death, myocardial infarction and target vessel revascularization) were assessed at 12 months after the procedure. Results: Clinical follow-up at 12 months was available in 90.8%. Female, hypertension, elderly patients and multi-vessel diseases were common in diabetic group than in non-diabetic group. Pre-interventional reference vessel diameter and stent size were smaller in diabetic group. The major adverse cardiac event (MACE) rate was similar during hospitalization. However, cumulative 12-month MACE was significantly higher in diabetic group. Conclusions: Although short-term outcomes were similar in diabetic and non-diabetes, the 12-month MACE was significantly worse in diabetic group.