PURPOSE: To analyze incremental information derived from routinely obtained chest computed tomographic (CT) scans compared with chest radiographs in newly diagnosed non-Hodgkin lymphoma and the effect of this information on staging and therapy. MATERIALS AND METHODS: Abnormalities on chest radiographs and CT scans obtained at specific sites were prospectively identified in 181 consecutive patients with no previous treatment When discrepant information was found, the effect on staging and treatment was determined. RESULTS: CT and chest radiographic findings were negative in 99 (55%) patients. CT findings were positive and chest radiograph findings were negative in 17 (9%). Both chest radiograph and CT findings were positive in 65 (36%) patients, 16 with identical sites of disease and 49 with more extensive intrathoracic disease at CT. Most stage changes occurred in the diffuse large cell histologic subtype. CONCLUSION: Although routine chest CT findings increased stage of disease in some patients, it had no effect on initial treatment of newly diagnosed non-Hodgkin lymphoma at this institution.