Rationale: Monoamine oxidase B (MAO-B) activity is reduced in smokers. A MAO-B inhibitor alone or co-administered with nicotine may mimic the effects of smoking and be a candidate drug for smoking cessation. Objective: This study aims to determine the efficacy and safety of EVT302, a selective reversible MAO-B inhibitor, alone and on top of nicotine patch (NP) in smoking cessation. Methods: This was a randomised, double blind, placebo-controlled phase II, multicentre trial. Smokers (≥10 cigarettes/day) received either EVT302 ( N = 145) or placebo ( N = 145), or EVT302 ( N = 61) or placebo ( N = 61) on top of open label NP 21 mg/day for 8 weeks. The main comparison was between EVT302 and placebo without NP. The primary outcome measure was end-of-treatment 4-week continuous abstinence rate (CAR). Secondary outcome measures: point prevalence abstinence rate, saliva cotinine concentrations in the groups without NP, urge to smoke, nicotine withdrawal symptoms and assessment of subjective effects of cigarettes. Results: The 4-week CAR was 15.2 % in the placebo, 17.2 % in the EVT302, 26.8 % in the NP + placebo and 32.8 % in the NP + EVT302 groups, respectively. There was no difference between EVT302 and placebo either alone (adjusted OR: 1.45, 95 % CI: 0.65-3.26) or when co-administered with NP. No statistically significant difference occurred for the secondary outcome measures. Conclusions: The selective, reversible MAO-B inhibitor EVT302 was not superior to placebo in helping smokers quit, in line with data with selegiline and confirms that MAO-B inhibitors are not effective in smoking cessation. Co-administration of NP does not provide a supplementary benefit. [ABSTRACT FROM AUTHOR]