Background: A previous Phase IIIb study (NCT01462929) in patients with moderate to severe COPD demonstrated that 6 weeks of treatment with aclidinium led to improvements in 24-hour bronchodilation comparable to those with tiotropium, and improvement of symptoms versus placebo. This post hoc analysis was performed to assess the effect of treatment in the symptomatic patient group participating in the study., Methods: Symptomatic patients (defined as those with Evaluating Respiratory Symptoms [E-RS™] in COPD baseline score ≥10 units) received aclidinium bromide 400 μg twice daily (BID), tiotropium 18 μg once daily (QD), or placebo, for 6 weeks. Lung function, COPD respiratory symptoms, and incidence of adverse events (AEs) were assessed., Results: In all, 277 symptomatic patients were included in this post hoc analysis. Aclidinium and tiotropium treatment improved forced expiratory volume in 1 second (FEV 1 ) from baseline to week 6 at all time points over 24 hours versus placebo. In addition, improvements in FEV 1 from baseline during the nighttime period were observed for aclidinium versus tiotropium on day 1 (aclidinium 157 mL, tiotropium 67 mL; P <0.001) and week 6 (aclidinium 153 mL, tiotropium 90 mL; P <0.05). Aclidinium improved trough FEV 1 from baseline versus placebo and tiotropium at day 1 (aclidinium 136 mL, tiotropium 68 mL; P <0.05) and week 6 (aclidinium 137 mL, tiotropium 71 mL; P <0.05). Aclidinium also improved early-morning and nighttime symptom severity, limitation of early-morning activities, and E-RS Total and domain scores versus tiotropium (except E-RS Chest Symptoms) and placebo over 6 weeks. Tolerability showed similar incidence of AEs in each arm., Conclusion: In this post hoc analysis of symptomatic patients with moderate to severe COPD, aclidinium 400 μg BID provided additional improvements compared with tiotropium 18 μg QD in: 1) bronchodilation, particularly during the nighttime, 2) daily COPD symptoms (E-RS), 3) early-morning and nighttime symptoms, and 4) early-morning limitation of activity., Competing Interests: Disclosure JB has received consulting fees, speaker’s fees, and travel expenses from AstraZeneca and has also received compensation for organizing or participating in advisory boards for Cytos, Boehringer Ingelheim, Almirall, AstraZeneca, Novartis, and Revotar Biopharmaceuticals. The institution where JB is currently employed has received compensation for the design, performance, or participation in single or multicenter clinical trials in the past 5 years from several companies including Almirall, Altana, AstraZeneca, Boehringer Ingelheim, Cytos, GSK, Meda Pharmaceuticals, Merck Sharp & Dohme, Mundipharma, Novartis, Pfizer, and Revotar Biopharmaceuticals. RM has received consulting fees, speaker’s fees, and travel expenses from Boehringer Ingelheim and has also received compensation for participating in advisory boards for Boehringer Ingelheim, Almirall, AstraZeneca, and Novartis. Furthermore, RM has received compensation for participation in multicenter clinical trials in the past 5 years from several companies including Almirall, AstraZeneca, Boehringer Ingelheim, GSK, Merck Sharp & Dohme, Mundipharma, Novartis, Pearl, Roche, and Takeda. A-MK is a current employee of Pulmonary Research Institute at LungenClinic Grosshansdorf; the institution received compensation for the design of and/or participation in clinical trials from Almirall, AstraZeneca, Boehringer Ingelheim, GSK, Novartis, Pfizer, Infinity Pharmaceuticals, TEVA, Sterna Biologicals, Chiesi, Bayer, and Takeda. Furthermore, A-MK has received consulting fees, and speaker’s fees from AstraZeneca, Boehringer Ingelheim, and Roche. FC and EGG are employees of AstraZeneca PLC, Barcelona, Spain, and former employees of Almirall S.A., Barcelona, Spain.