OBJECTIVES: To estimate the relative efficacy of a new long-acting muscarinic antagonist (LAMA), aclidinium bromide 400 µg BID (AB400), to tiotropium bromide 18 µg (TIO18) and 5 µg (TIO5) QD in patients with COPD. METHODS: A systematic literature search using a predefined strategy in MEDLINE©, EMBASE© and the Cochrane Library identified 21 unique placebo-controlled RCTs: TIO18 (16 trials), TIO5 (3 trials) and AB400 (2 trials). Outcomes were change from baseline (CFB) in lung function (trough FEV1), disease-specific health status by St. George’s Respiratory Questionnaire (SGRQ) total score, and breathlessness by Transition Dyspnea Index (TDI) focal score, at 12 and 24 weeks. All trials were analysed simultaneously using a Bayesian network meta-analysis and relative treatment effects between all regimens were obtained. Meta-regression techniques were included to investigate dissimilarities in study design and patient characteristics across trials. RESULTS: In line with the pivotal trials, AB400 was shown to be more efficacious than placebo on all evaluated endpoints. AB400 showed comparable but numerically greater improvements at 12 weeks compared to TIO18 in trough FEV1 [difference in CFB (95% Credible Interval) 0.001L (-0.03,0.03)], SGRQ total score [-0.85 (-3.41,1.75)] and TDI focal score [0.06 (-0.41,0.52)].  Similar but numerically greater differences were also seen for AB400 versus TIO18 at 24 weeks in trough FEV1 [0.02L (-0.02,0.08)], SGRQ total score [-1.84 (-4.21,0.51)] and TDI focal score [0.10 (-0.53,0.73)]. Additionally, AB400 showed similar improvements on these same endpoints versus TIO5 (where data was available). Meta-regression analyses, correcting for differences in treatment patterns (concurrent ICS, LABA treatment) and COPD severity (baseline FEV1 percent predicted) across the trials, showed comparable findings as the base case analysis. CONCLUSIONS: This meta-analysis suggests that maintenance treatment with aclidinium 400 µg BID results in comparable improvements in lung function, health status, and breathlessness as tiotropium 18 µg and 5 µg QD in COPD patients.