Background Drug-eluting stent (DES) has been used widely for the treatment of patients with acute coronary syndrome with or without diabetes mellitus during percutaneous coronary intervention (PCI), but its long-term safety and efficacy in diabetic patients with acute ST elevation myocardial infarction (STEMI) remain uncertain. This study aimed to investigate the clinical outcomes after primary coronary intervention with DES implantation for diabetic patients with acute STEMI, compared with non-diabetic counterparts.Methods From December 2004 to March 2006, 56 consecutive diabetic patients (diabetic group) and 170 non-diabetic patients (non-diabetic group) with acute STEMI who underwent primary PCI with DES implantation in 3 hospitals were enrolled. Baseline clinical, angiographic, and procedural characteristics, as well as occurrence of major adverse cardiac event (MACE) including cardiac death, non-fatal recurrent myocardial infarction (re-MI) and target vessel revascularization (TVR) during hospitalization and one-year clinical follow-up were compared between the two groups.Results Patients in diabetic group were more hyperlipidemic (69.6% and 51.8%, P=0.03) and had longer time delay from symptom onset to admission ((364±219) minutes and (309±223) minutes,P=0.02) than those in non-diabetic group.The culprit vessel distribution, reference vessel diameter, and baseline TIMI flow grade were similar between the two groups, but multi-vessel disease was more common in diabetic than in non-diabetic group (82.1% and 51.2%, P＜0.001).Despite similar TIMI flow grades between the two groups after stenting, the occurrence of TIMI myocardial perfusion grade (TMPG)≥2 was lower in diabetic group (75.0% vs 88.8% in non-diabetic groups, P=0.02). The MACE rate was similar during hospitalization between the two groups (5.4% vs 3.5%, P=0.72), but it was significantly higher in diabetic group (16.1%) during one-year follow-up, as compared with non-diabetic group (6.5%, P=0.03). The cumulative one-year MACE-free survival rate was significantly lower in diabetic than in non-diabetic group (78.6% vs 90.0%, P=0.02).Angiographic stent thrombosis occurred in 5.4% and 1.2% of the patients in diabetic and non-diabetic group, respectively (P=0.19). All of these patients experienced non-fatal myocardial infarction.Conclusions Although the early clinical outcomes were similar in diabetic and non-diabetic patients with acute STEMI treated with DES implantation, the cumulative MACE-free survival at one-year follow-up was worse in diabetic than in non-diabetic patients. More effective diabetes-related managements may further improve the clinical outcomes of diabetic cohort suffering STEMI.