The effective prevention of exacerbations in patients with chronic obstructive pulmonary disease (COPD) has the potential to improve patients' health-related quality of life, reduce rates of hospitalisation and mortality and lower healthcare costs. Several pharmacological agents, including inhaled corticosteroid/long-acting beta2-agonist combination therapies, have demonstrated beneficial effects on COPD exacerbations. The number needed to treat (NNT) analysis is a simple, concise method that allows physicians to quantify directly the benefits that alternative treatment options have on disease outcomes in terms of the number of patients who need to be treated before a benefit is observed. This review evaluates the applicability and clinical relevance of NNT analysis for determining the effectiveness of combination therapies against COPD exacerbations, focusing on budesonide/ formoterol in the same inhaler. Physicians are encouraged to consider NNT data within the context of their limitations and in conjunction with other analytical methods when selecting treatments for patients with COPD.