Bare metal stents (BMS) have practically been replaced by drugeluting stents (DES), as previous trials have shown a reduction of in-stent-restenosis and repeat revascularisation. To prevent the formation of neointimal hyperplasia, current DES are coated with a thin polymer film which regulates the amount of drug that is eluted into the treated vessel. Accumulating evidence shows that permanent polymer could trigger a chronic inflammatory response, which is characterised by a delayed re-endothelialisation, resulting in incomplete strut coverage and the potential for late stent thrombosis (LST). Based on these considerations, newer generations of DES have focused on the safety profile, changing from durable polymer to biodegradable polymer and ultimately to polymer-free stents in order to diminish vascular inflammation further. The assessment of vascular repair (i.e., to quantify strut coverage) after stent implantation by using optical coherence tomography (OCT) has shown that strut coverage is higher in biodegradable polymer stents than in permanent polymer stents. So far, there have been only a few studies assessing strut coverage at a very short-term time point (three months). Also, there have been only two OCT studies which examined the patterns of strut coverage in polymer-free stents. In the present study, the polymer-free stent with a nano-sized-pore surface has been considered as an alternative modality of local drug delivery. We hypothesised that polymer-free stents have an early arterial healing, thereby reducing the risk of late stent thrombosis, and a controlled growth of neointima, which may reduce the likelihood of restenosis. In our present study, we sought to evaluate the extent of three-month neointimal coverage after the implantation of polymer-free nano-sized-pore surface sirolimus-eluting stents (SES) (Nano+™, Lepu Medical, Beijing, China).