Oxidative stress is implicated in the pathogenesis of respiratory diseases, such as COPD and its comorbidities, asthma, idiopathic pulmonary fibrosis and radiation pneumonitis. Antioxidants drugs, such as small molecule thiols, nuclear erythroid-2 related factor 2 activators and catalytic enzyme mimetics have been developed to target oxidant-dependent mechanisms. The therapeutic effects of antioxidants have been generally disappointing. A small number of antioxidants are approved for clinical use, such as the small molecule thiol N-acetyl-l-cysteine for chronic obstructive pulmonary disease, and in the United States, the superoxide dismutase mimetic AEOL 10150 for severe radiation pneumonitis. The future use of antioxidants for the treatment of chronic respiratory diseases may require a precision medicine approach to identify responsive patients.