OBJECTIVES: Aclidinium/formoterol 400/12 µg (FDC 400/12 µg), is a long-acting muscarinic antagonist (LAMA) and a long-acting β2-agonist (LABA) in a fixed-dose combination used in the management of patients with chronic obstructive pulmonary disease (COPD). This study aimed to assess the cost-effectiveness of FDC 400/12 µg against the LAMA, aclidinium bromide 400 µg (AB 400 µg). METHODS: A 5 health state Markov transition model, with monthly cycles, was developed using MS Excel to simulate the clinical course of patients with moderate to severe COPD treated with FDC 400/12 µg versus AB 400 µg. Health states were based on severity levels defined by GOLD 2010 criteria. The analysis was a head to head comparison without step-up-therapy, from the NHS Scotland perspective, over a 5 year time horizon. Clinical data on the initial lung function improvement was provided by a pooled analysis of the ACLIFORM and AUGMENT trials. Resource use (management and event costs) and utilities were health state specific. Costs and effects were discounted at an annual rate of 3.5%. The outcome of the analysis was cost (£) per quality adjusted life year (QALY) gained. The analysis included one way and probabilistic sensitivity analyses to investigate the impact of parameter variability on model outputs. RESULTS: FDC 400/12 µg provided marginally higher costs (£41) and more QALYs (0.014), resulting in an incremental cost-effectiveness ratio of £2,976. Sensitivity analyses indicated results were generally robust to key parameter variation. The main drivers were mean baseline FEV1, risk of exacerbation, FEV1 improvement of FDC 400/12 µg and lung function decline.  The probability of FDC 400/12 µg be cost-effective (using a willingness to pay threshold of £20,000/QALY) versus AB 400 µg was 79%. CONCLUSIONS: In the Scottish setting, aclidinium/formoterol 400/12 µg can be considered a cost-effective treatment option in patients with COPD versus aclidinium 400 µg.