Positron emission tomography is a powerful quantitative molecular imaging technique that is complementary to structural imaging techniques for purposes of disease detection and characterization. This review article provides an overview of the applications of positron emission tomography for evaluation of patients with nononcological diseases that may be encountered in the thorax, such as infection, sarcoidosis, idiopathic interstitial pneumonia, adult respiratory distress syndrome, chronic obstructive pulmonary disease, and atherosclerosis among others.