Characterization of neointimal tissue is essential to understand the patho-physiology of in-stent restenosis (ISR) after drug-eluting stent (DES) implantation. Using optical coherence tomography (OCT), we compared the morphologic characteristics of in-stent neointimal tissue from ISR lesions with those of non-ISR lesions after DES implantation. The DES were coated with sirolimus (n=52), paclitaxel (n=57), zotarolimus (n=84), or everolimus (n=32). ISR was defined as ���50% diameter stenosis at the follow-up angiogram. Lesions with ���10% neointimal burden [(neointima area��100)/(stent area)], as determined by OCT, were included in this study. A follow-up OCT (mean follow-up duration: 12.0 짹10.5 months) was performed in 209 patients with 225 lesions (ISR lesions, n=192; non-ISR lesions, n=33). Qualitative OCT was used to assess tissue structure, backscatter, visible microvessels, and presence of intraluminal material. The following characteristics were more common in ISR lesions than in non-ISR lesions: heterogeneous or layered tissues (78.8% vs. 22.9%, p<0.001), low backscatter (60.6% vs. 20.8%, p<0.001) and microvessels (48.5% vs. 5.7%, p<0.001). The independent predictors for heterogeneous or layered neointimal tissues were: increased neointima burden (OR=1.218, 95% CI=1.096-1.354; p<0.001), lumen area (OR=4.672, 95% CI=1.371-15.914; p=0.014), and hypertension (OR=0.415, 95% CI=0.186-0.926; p=0.032). This follow-up OCT study demonstrated that morphologic characteristics of neointimal tissues of ISR lesions differ from those of non-ISR lesions.