Asthma and chronic obstructive pulmonary disease are both common conditions with an increasing prevalence worldwide. Inhaled therapy for these conditions has a number of advantages over systemic therapy, including reduced side effects and quicker onset of action. The effective use of inhaled therapy is critically dependent upon the nature of the drug-delivery system and the ability of the patient to use the system correctly. There are a wide number of inhaler devices on the market, each with positive and negative aspects. A crucial part of patient care is to ensure that the choice of inhaler device for the individual is an effective therapy. There are a number of interventions that can help with the choice of inhaler device and also improve the ability of the patient to use inhaled therapy. Inhaler technique training needs to be a cornerstone of the care of patients with asthma or chronic obstructive pulmonary disease to ensure optimal therapy.