People with diabetes mellitus are more prone to coronary heart disease, stroke, and peripheral vascular disease, and diabetes mellitus has been regarded as an independent risk factor for the progression of coronary artery disease. Several studies have been reported that diabetes increased the risk of cardiovascular mortality in both men and women. With the introduction of drug-eluting stents (DESs), the angiographic rates of restenosis at later months have reduced dramatically in several studies. However, even with DESs, diabetic patients showed increased rates of restenosis and late loss index compared with nondiabetic patients. Diabetes has been considered to be a predictor of poor prognosis after percutaneous coronary intervention with drug-eluting stents. Long-term clinical and angiographic outcomes after percutaneous coronary intervention (PCI) with drug-metal stents (DESs) have been demonstrated to be worse in diabetic patients compared with nondiabetic patients. In the era of DESs, no study has demonstrated the clinical and angiographic outcomes in diabetic patients after DES implantation by using optical coherence tomography (OCT).