Background: To evaluate the neointimal conditions of everolimus-eluting stents (EESs) implanted in culprit lesions of patients with acute coronary syndrome (ACS) compared with stable angina pectoris (SAP) using optical coherence tomography (OCT). EESs are second-generation drug-eluting stents that have recently been shown to be useful in patients with ACS as well as in patients with SAP. However, few studies have analyzed the intra-stent conditions of EESs that can lead to favorable results in such ACS lesions. Methods:We evaluated 41 ACS patients with EES implantation (age, 66.7  10.3 years) and 59 SAP patients enrolled as controls (age, 68.3  10.7 years). OCT examinations were performed after 9 months of follow-up after stent implantation, and the condition of the neointimal coverage over every stent strut was assessed in 1-mm intervals. In addition, neointimal thickness (NIT) over each strut was measured and tissue characteristics were examined. Results: There was no significant difference in mean NIT between the ACS (90.8 ± 88.2 mm) and SAP (87.3 ± 74.2 mm, p = 0.11) group. The rate of uncovered struts was significantly lower in the ACS group (11.5%) than in the SAP group (12.5%, p = 0.03). Neointimal tissue characteristics were also similar between groups. Conclusions: Vascular responses after EES implantation differed significantly between ACS and SAP lesions using OCT. However, these differences were considered small in clinical terms. Our OCT data support the favorable results of patients with EES implantation at mid-term follow-up, even in those with ACS.