COPD is often misdiagnosed and inappropriately treated in many patients. COPD is a distinct disease from adult-onset asthma; however, some patients with COPD may present with several forms of airway disease described as asthma-COPD overlap (ACO). Bronchodilators and inhaled corticosteroids (ICS) both have a place in standard maintenance treatment of COPD and asthma; however, recommendations for use differ widely. In patients with COPD, long-acting bronchodilators are effective initial monotherapy treatment, whereas ICS monotherapy is recommended as initial treatment in patients with asthma. Clinicians need to be confident in their diagnosis to ensure that correct treatment is given because misguided treatment decisions can result in significantly increased safety risks for patients. This review highlights the differences in diagnosis and treatment between COPD, asthma, and ACO and discusses the data supporting guideline recommendations for use of bronchodilators in COPD treatment in contrast to asthma or ACO.