OBJECTIVE Computed tomography is commonly used in the diagnosis of pediatric lung disease. Although the radiation is not negligible, the yield has never been studied. METHODS Clinical and imaging data were collected for all children who underwent chest computed tomography, as part of the diagnostic process. Cases were grouped according to type of lung disease, based on clinical data and the question addressed to the radiologist. A positive yield was defined as computed tomography providing >or=1 of the following: (1) a diagnosis, (2) a clinically important new finding that had not been recognized previously, (3) alteration of the plan for further evaluation or treatment, or (4) exclusion of lung disease. No yield was defined when computed tomography did not add new information and did not affect evaluation or treatment. RESULTS Ages ranged from 2 weeks to 16 years, and 59% were male. The overall positive yield was 61% (64 of 105 cases). Yields were relatively low, that is, 23% (8 of 35 cases) for the evaluation of diffuse lung disease, 46% (6 of 13 cases) for localized disease, 50% (6 of 12 cases) for pleural disease, and 98% (41 of 42 cases) for congenital malformations. CONCLUSIONS The yield of chest computed tomography depends on the type of disease. Computed tomography has a significant yield for congenital anomalies. The yield is particularly low in the evaluation of acquired diffuse pulmonary disease and is relatively low in acquired focal lung disease. We suggest that chest computed tomography be used more judiciously.