Recent research on asthma and COPD has concentrated in developing new inhalation delivery systems. Innovation has improved metered-dose, dry-powder, or breathe-actuated inhalers and nebulizers. The objective of this study was to review current literature on the different inhalation devices available in the market, and how their characteristics have asso- ciations with disease outcomes both for asthma and COPD. The main concerns have been to facilitate the drug’s administration for the patient, as measured by pharmacokinetics, safety, patient preference, medication adherence, quality of life, and costs. Medication adherence has a positive association with patient preference and ease of use of the device that admi- nisters the drugs for disease control. A good medication adherence can reduce exacerbation episodes, improving QOL, and reducing costs for respiratory diseases.