Background Weight gain following smoking cessation increases cardiovascular risk,but its effects on prognosis after percutaneous coronary intervention (PCI) remain unclear.This study aimed to investigate the relationship between weight gain post smoking cessation and one-year clinical outcome in patients who underwent PCI with drug-eluting stent (DES).Methods A total of 895 consecutive male smoking patients were divided into quitters (n=437) and continuers (n=458)according to their smoking status after PCI.Weight gain,major adverse cardiac events (MACE,including cardiac deaths,myocardial infarction and revascularization),and recurrent angina were recorded during follow-up for one year.Results Average weight gain in quitters was more than that in continuers (1.5 kg vs.-0.03 kg,P＜0.001).Weight was unchanged or increased by more than 1.5 kg in 78.17％ of continuers,while 50.57％ of quitters had a weight gain of less than 1.5 kg.Compared with continuers,MACE in quitters was significantly reduced after PCI (6.12％ vs.4.81％,P=0.049),especially recurrent angina (13.97％ in continuers vs.9.84％ in quitters,P=-0.027).After adjusting for weight gain and other factors,smoking cessation was independently associated with a lower risk of MACE and recurrent angina (OR=0.73,P=0.035).However,weight gain ＞1.5 kg (OR=1.55,P=0.026) could curtail the benefits from smoking cessation.Conclusions Weight gain may reduce the benefits of smoking cessation after PCI with DES implantation.Thus,although smoking cessation is recommended after PCI,weight control should also be highly encouraged for these patients.