Diabetes is associated with an increased risk of major adverse cardiac events after percutaneous coronary intervention. We compared clinical outcomes in patients with and without diabetes mellitus treated with the second-generation Endeavor zotarolimus-eluting stent (ZES) or the first-generation Cypher Select+ sirolimus-eluting stent (SES). We randomized 2,332 patients to treatment with ZESs (n = 1,162, n = 169 diabetics) or SESs (n = 1,170, n = 168 diabetics) and followed them for 18 months. Randomization was stratified by presence/absence of diabetes. The primary end point was major adverse cardiac events defined as a composite of cardiac death, myocardial infarction, or target vessel revascularization. Secondary end points included these individual end points plus all-cause mortality and target lesion revascularization. In diabetic patients, use of ZES compared to SES was associated with an increased risk of major adverse cardiac events (18.3% vs 4.8%, hazard ratio 4.05, 95% confidence interval 1.86 to 8.82), myocardial infarction (4.7% vs 0.6%, hazard ratio 8.09, 95% confidence interval 1.01 to 64.7), target vessel revascularization (14.2% vs 3.0%, hazard ratio 4.99, 95% confidence interval 1.90 to 13.1), and target lesion revascularization (12.4% vs 1.2%, hazard ratio 11.0, 95% confidence interval 2.59 to 47.1). In patients without diabetes differences in absolute risk decrease were smaller but similarly favored SES. In conclusion, implantation of ZESs compared to SESs is associated with a considerable increased risk of adverse events in patients with diabetes at 18-month follow-up.