Pharmacoepidemiology studies are of particular interest in the respiratory field and especially for inhaled drugs. In real-life, excessive use of rescue medications and under- or inappropriate-prescribing of preventer medications has been shown. In asthma and chronic obstructive pulmonary disease (COPD), the poor use of inhalation device is associated with uncontrolled diseases and occurrence of exacerbations. Inhalation treatments are directly delivered within the lung and are generally considered as safe. However, systemic adverse drug reactions that were not evidenced in clinical trials may be observed after a long-term treatment.