Background and objective: The efficacy of inhaled corticosteroids (ICS) in asthma exacerbation are yet to be clarified. The aim of this study was to investigate the efficacy of nebulized ICS in children with moderate-tosevere acute exacerbation of asthma in an emergency room setting in order to elucidate the potential use of ICS as the first-line therapy in the management of acute exacerbation of asthma. Methods: This was a prospective, randomized, double-blind, placebo-controlled study. Paediatric patients with moderate-to-severe acute exacerbation of asthma in emergency room were randomized to receive nebulized salbutamol and ipratropium bromide, with the addition of nebulized high-dose budesonide (BUD group, n = 60) or normal saline (control group, n = 58), three doses in the first hour. Results: The improvement in forced expiratory volume in 1 s was similar in both groups at 0 h after three doses of nebulization, but there was significantly further improvement at 1 and 2 h in the BUD group (0.095 ± 0.062 L and 0.100 ± 0.120 L, respectively) compared with the control group (0.059 ± 0.082 L and 0.021 ± 0.128 L, respectively), P = 0.013 and 0.001, respectively. Complete remission rate was significantly higher (84.7% vs 46.3%, P = 0.004) and need for oral corticosteroids was significantly lower (16.9% vs 46.3%, P = 0.011) in BUD group than in control group. Conclusion: On the basis of nebulized short-acting bronchodilators, addition of nebulized high-dose budesonide resulted in clinical improvement in children with moderate-to-severe acute exacerbation of asthma, suggesting that nebulized high-dose ICS can be used as first-line therapy for non-life-threatening acute exacerbation of asthma in children.