Lung cancer is the most frequently diagnosed cancer in the world, and the leading cause of death from cancer. Radiology plays a critical role in the initial detection and diagnosis of thoracic malignancies, as well as in pretreatment staging, which is important in identifying patients with localized disease who are likely to benefit from surgical resection. Chest radiography and computed tomography (CT) have been the primary imaging modalities used to fulfill these roles. Positron emission tomography (PET) is rapidly emerging as a clinically useful noninvasive study that complements conventional radiologic imaging in the evaluation of patients with lung cancer. The role of magnetic resonance imaging (MRI) in this regard generally is limited; it is used primarily for specific problem-solving issues, such as the determination of chest wall or mediastinal invasion.