Mediastinal masses occur in both men and women of every age, and close to half of affected patients are asymptomatic. Screening of asymptomatic persons is not economically feasible. Symptomatic patients should be evaluated initially with posteroanterior and lateral chest radiographs. Additional imaging techniques may be required in patients suspected of having a mediastinal mass, when there is a questionable abnormality seen on chest radiographs or when local or systemic symptoms suggest a mediastinal mass. These techniques include oblique views, over-penetrated radiographs, and fluoroscopy of the chest. Computerized tomography of the chest is the imaging modality of choice for further assessment of a mediastinal mass. It can also be an important adjunct in radiotherapy portal planning. The use of other imaging modalities depends on the location of the tumor, the equipment available, and the expertise of local radiologists. In following up treated patients for disease recurrence, periodic chest radiographs are usually sufficient. Computerized tomography scans, because of their expense, should only be obtained as a baseline after completion of therapy or in patients with a suspected relapse.