Background: Acute coronary syndrome (ACS) has a different pathophysiology from stable angina and the different pattern of neointmal hyperplasia (NIH) and malapposition. Therefore, we compared NIH pattern and malapposition at 9 months after implantation between ACS and non-ACS using OCT. Method: Optical coherence tomography (OCT) was performed at 9-month with 39 ACS (13 in sirolimus eluting stent (SES), 15 in Paclitaxel eluting stent (PES) and 11 in Zotarolimus eluting stent (ZES)) and 34 non-ACS (14 in SES, 10 in PES and 10 in ZES). NIH thickness, percent NIH area and rate of malaaposition were measured at each stent strut and corss section. Results: In total, 16398 struts in 1698-mm single-stented segments were analyzed. Overall, NIH thickness and percent NIH area were not different between ACS and non-ACS (173 짹 100 vs. 178 짹 137 關m, p = 0.602 and 21 짹 13 vs. 21 짹 11 %, p =0.940) and rates of malapposition and exposed struts were also not significantly different (2.1 vs. 0.5 %, p=0.118 and 5.0 vs. 2.4 %, 0.264). According to the type of stents, SES has different features according to presence of ACS compared to other 2 drug eluting stents (DESs, Table 1). Conclusion: Neointimal coverage and malapposition rate at 9-month after stent implantation was not significantly defferent between ACS and non-ACS. But, SES has somewhat different patterns of NIH. Therefore, present study suggested that neointimal coverage and malapposition might be influenced by type of DESs more than clinical presentation.