Summary Background The bronchodilatory effect of mometasone furoate/formoterol fumarate (MF/F) administered by metered-dose inhaler (MDI) with or without a spacer has not been evaluated previously in children aged 5–11 years. Methods This was a randomized, multicenter, placebo-controlled, single-dose, four-period crossover study. Children with persistent asthma aged 5–11 years participated in this study. Subjects used inhaled corticosteroids with/without long-acting beta-2 agonists for 12 weeks before enrollment and at screening had forced expiratory volume in 1 sec (FEV1) ≥70% predicted. Subjects received MF/F MDI 100/10 µg with/without spacer (AeroChamber Plus® with Flow-Vu® Anti-Static Valved Holding Chamber), F-Dry Powder Inhaler (F-DPI) 10 µg, and placebo MDI with/without spacer in separate treatment periods. The primary endpoint was FEV1 area under the curve from 0 to 12 hr (AUC0–12hr) for the comparison of MF/F with spacer versus placebo. Secondary measurements included MF/F without spacer versus placebo, as well as MF/F with spacer versus MF/F without spacer, and F-DPI versus placebo. Analysis was performed with an analysis of covariance model for a crossover study. Results Data from 87 subjects were analyzed. MF/F with spacer demonstrated a larger change in mean FEV1 AUC0–12hr versus placebo (115 vs. −9 mL), with a treatment difference of 124 mL (95% CI 94–154, P