The Genuair ® inhaler is a new multidose dry powder inhaler for the delivery of aclidinium bromide – a novel, long-acting, muscarinic antagonist in development for the treatment of chronic obstructive pulmonary disease (COPD). The primary aim of this study was to assess the inspiratory flow characteristics through Genuair ® in patients with moderate or severe COPD.Using a three-period cross-over design, 48 patients were randomised to inhale placebo powder through Genuair ® , HandiHaler ® A (slow, deep inhalation as per manufacturer's instructions) or HandiHaler ® B (fast, forceful inhalation). Three measurements of peak inspiratory flow (PIF), 10min apart, were recorded for each method of administration.The highest and average PIFs for the three attempts (mean±standard deviation) generated through the Genuair ® inhaler were 97.7±15.7 and 92.0±15.4L/min, respectively. Furthermore, 97% of inhalations with the Genuair ® inhaler were successful (activation of trigger threshold mechanism) and optimal (PIF≥45L/min). The highest and average PIFs generated through HandiHaler ® A and B were significantly lower than with the Genuair ® inhaler.In conclusion, patients with moderate or severe COPD were able to generate sufficient inspiratory airflow through the Genuair ® inhaler to reliably inhale the full dose and reset the inhaler.