Pressure on healthcare budgets is increasing, while at the same time patent protection for many branded inhaled medications has expired, leading to the development and growing availability of generic inhaled medicines. Generic inhaled drugs are therapeutically equivalent to original branded options but may differ in their formulation and inhalation device. This new situation raises questions about the potential impact of switching from branded to generic drug/inhaler combination products in patients with asthma or COPD, with or without their consent, in countries where this is permitted. Inhalation devices, particularly dry powder inhalers, vary markedly in their design, method of operation and drug delivery to the lungs. Current guidelines stress the importance of training patients how to use their inhalers but offer little or no guidance on how this should be achieved. Non-adherence to therapy and incorrect inhaler usage are recognised as major factors in poorly or uncontrolled asthma and COPD and switching patients to a different inhaler device may exacerbate these problems, particularly in patients who disagree to switch. Where switching is permitted or mandatory, adequate patient instruction and follow-up monitoring should be provided routinely.