The efficacy of inhaled corticosteroids (ICSs)/long-acting beta2-agonist (LABA) treatment in patients with asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) compared to patients with COPD alone has rarely been examined. This study aimed to evaluate the clinical efficacy for the improvement of lung function after ICS/LABA treatment in patients with ACOS compared to COPD alone patients.