This study aimed to evaluate the impact of vascular response assessed by intravascular ultrasound (IVUS) imaging on clinical outcomes in elderly patients (≥ 75 years) undergoing percutaneous coronary intervention (PCI) for de novo lesions with sirolimus-eluting stent (SES) implantation. Repeat coronary angiography with IVUS was performed 1 year after SES-based PCI for de novo lesions in 136 elderly patients (≥ 75 years) and 427 younger counterparts (< 75 years) (219 lesions and 635 lesions, respectively). Major adverse cardiac events (MACE) including cardiac death, non-fatal myocardial infarction, and target lesion revascularization (TLR) during 2-year follow-up were recorded. Despite similar angiographic in-stent restenosis and TLR and IVUS-detected incomplete stent apposition (ISA), absolute intimal hyperplasia and percentage of volumetric obstruction were lower in elderly than in younger patients. At 2-year follow-up, cumulative survival freedom from composite death and myocardial infarction or MACE was significantly reduced in elderly patients, but very late stent thrombosis was similar in the two groups. Cox proportional hazards model identified age, diabetes, left ventricular ejection fraction, lesion length,minimal stent cross-sectional area and plaque progression as independent predictors of non-fatal myocardial infarction or mortality. In elderly patients undergoing SES-based PCI, despite similar TLR, neointimal hyperplasia was significantly lower than in younger patients. IVUS measurements except for minimal stent cross-sectional area did not correlate with stent thrombosis and clinical outcomes at 2 years.