Background and Objectives: There have been little data regarding major determinants for the uncovered stent struts after DES implantation on OCT in the largest study patients. We investigated major determinants for the incomplete neointimal coverage of the stent strut on optical coherence tomography (OCT) after drug-eluting stent (DES) implantation in the real world practice. Methods: A total of 279 lesions in 261 patients treated with various DESs from the Yonsei OCT registry were divided into two groups based on the highest quartile value (5.4%) of % uncovered struts, calculated as percent ratio of uncovered struts to total struts in all cross-sections on OCT; the uncovered group (highest quartile with % uncovered struts ���5.4%, n=70) versus the covered group (the remaining lower quartiles with % uncovered struts <5.4%, n=209). Results: The uncovered group was more likely to have complex lesions, smaller reference vessel diameter, smaller and longer stents implanted, and more use of sirolimus-eluting stent and less use of zotarolimus-eluting stent, compared with the covered group. By multivariate analysis, the most significant determinant for the uncovered stent struts was the DES type (odds ratio [OR] =2.61, 95% confidence interval [CI] =1.81-3.76, p<0.001). The use of sirolimus-eluting stent (SES; OR=2.47, p=0.021) and zotarolimus-eluting stent (ZES; OR=0.01, p=0.002) was the only significant risk and protective factor for the uncovered stent struts, respectively (See figure). Conclusions: This real world OCT study demonstrated that the DES type might be the more important determinant for the uncovered struts than any other clinical and angiographic factors.