After the development of second generation drug-eluting stent (DES), clinical outcomes including in-stent restenosis have been dramatically improved in patients with coronary artery disease undergoing percutaneous coronary intervention (PCI) compared with bare metal stent or first generation DES era. However, interventional cardiologist still concern about late adverse cardiac events including stent thrombosis (ST) in patients who received implantation of permanent metallic stent. Bioresorbable scaffold (BRS) have been developed to provide mechanical support and drug-delivery function similar to those of DES for approximately 1 year, followed by complete bioresorption over several years. It has the advantages of reducing the risk of late ST and maintaining of normal vascular function because these novel devices are expected to leave no permanent materials within the vessel. Although there was no significant difference from previous randomized controlled studies for evaluating the clinical outcomes at 1-year between BRS and DES, recently documented ARSORB II trial, which compared 3-year outcomes between BRS and DES, show that patients treated with BRS had a higher risk of device-oriented composite endpoint mainly driven by target vessel myocardial infarction (MI) compared to those with DES. In addition, in several case reports, the late ST after discontinuation of dual anti-platelet therapy (DAPT) was reported in patients who underwent BRS implantation. Therefore, the efficacy of extended DAPT and needs for optimal DAPT duration in patients treated with BRS have been emerged. In the DAPT study, randomized controlled trial including approximately 10,000 patients, DAPT beyond 1 year after placement of a DES, as compared with aspirin therapy alone, significantly reduced the risks of major adverse cardiovascular and cerebrovascular events (MACCE) and ST. However, extend use of DAPT increases bleeding risk and cost. Endoscopic, dental, and surgical procedures are often delayed due to extended DAPT, which may affect the patient's quality of life. In addition, there was no significant difference in all-cause mortality between extended DAPT and aspirin monotherapy in the DAPT study because of increased bleeding risk in extended DAPT group. Therefore, to determine the optimal or minimal necessary duration of DAPT is very important. The other important issue is that which antiplatelet agent is more appropriate after DAPT. In CAPRIE (Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events) trial, clopidogrel showed a superior efficacy in preventing ischemic events compared with aspirin and the incidence of gastrointestinal bleeding was significantly lower with clopidogrel than with aspirin. Moreover, clopidogrel monotherapy was associated with a reduced risk of ischemic events without increased bleeding risk compared with aspirin monotherapy in patients receiving DES after 12-month DAPT. However, current guidelines still recommend aspirin monotherapy after 6-12 months of DAPT in patients treated with DES, there were no data for evaluating the optimal duration of DAPT and preferred choice of monotherapy in patients treated with BRS. Through results of previous studies, the authors postulated that P2Y12 antagonist monotherapy, which might have superior ability to prevent ischemic event compared to aspirin monotherapy, had similar risk of ischemic events with lower risk of bleeding complication compared with extended DAPT in patients who received BRS implantation with 12-month DAPT. Therefore, in the SMART-CHOICE II trial, we will test noninferiority of P2Y12 antagonist monotherapy compared with aspirin plus P2Y12 antagonist after 12-month of DAPT in patients treated with BRS.