Because oxidative stress is such a common factor of lung diseases, we cannot help asking why so many diseases are caused by the same oxidative stress. It is likely to be a consequence of diversity in sources and location of oxidative stress, and concomitant factors. The aim of this forum is to characterize the disease-specific involvement of oxidative stress and to make use of it for therapeutics. It is also of note that oxidative-stress biomarkers are useful tools for disease management. Exhaled nitric oxide has been established as a marker of bronchial asthma in clinical practice. By using recent noninvasive techniques, such as exhaled breath condensate, other markers of lipid peroxidation or antioxidants are now under evaluation. Antioxidant therapy, as represented by N-acetylcysteine, has widely been tested as a treatment for lung disorders, but it has had limited success in clinical practice. The clinical outcome might be improved by combination therapy or better patient selection. Novel antioxidant drugs are also under investigation. Molecular targeted therapy against redox-sensitive signaling pathways could be an alternative therapeutic approach. Moreover, disease-specific pathways have been identified whose regulation could be more efficient and less toxic than regulating universal pathways.