Background: ZES have different characteristics with biocompatible polymer and rapid drug elution compared to the 1st generation drug-eluting stents (DESs). We performed this study to investigate the vascular response in early period after Zotarolimus-eluting stents (ZES) implantation. Results - The ENDEAVOR OCT trial (Evaluation in 3 moNths Duration of nEointimAl coVerage after zOtaRolimus-eluting stent implantation by Optical Coherence Tomography [OCT]) is a prospective, single center study evaluating vascular healing patterns using OCT at 3-month after stent implantation. A total of 31 ZESs in 30 patients underwent serial OCT at immediately post-procedure and at 3-months. Neointimal growth and malapposition were analyzed at each stent strut of cross-sectional OCT images at 0.5-mm intervals. The incidence of malapposition at baseline and at 3-month was 6.0% and 0.2 %, respectively. No late acquired malappositions were detected at 3-month. Of 31 stents, 27 (87.1%) were covered completely with neointima, but the remaining 4 stents had 2 (0.8%), 4 (0.9%), 4 (1.2%) and 6 (1.4%) uncovered struts. Overall mean percentage of covered stent struts was 99.9짹0.4%. This finding was consistent among patients with acute coronary syndrome and stable angina pectoris (99.9짹0.3 % vs. 99.9짹0.4 %, p= 0.92). Intracoronary thrombi were documented in one stent (3.2%) among 31 stents. Conclusion – Neointimal coverage of stent struts was nearly complete and late acquired malapposition was not found at 3-month after ZES implantation. Therefore, the current study demonstrated that ZES might be related to a favorable in vivo vascular response even at 3-month after stent implantation.