Until recently, a definitive diagnosis of lipoma in the thorax could only be established by thoracotomy. We undertook this study to determine if chest CT could provide such an answer. Among 4,000 chest CT scans, six patients were found to have lipoma according to the following selected criteria: CT features of a pleural mass; a lesion showing completely homogeneous density with CT numbers indicating fat, and exclusion of other fatty lesions. In these six patients, the lipoma was an incidental finding, four were men, the mean age was 64.3 years, one-half were obese, and none had chest pains or dyspnea. Lesions varied in size from 2 to 4 cm and occurred along the chest wall. The CT numbers of the masses ranged from -54 to -129. None developed malignancy. In conclusion, we recommend clinical and chest CT follow-up for the asymptomatic patient who fulfills our CT criteria for lipoma. Biopsy or resection is recommended for lesions that are inhomogeneous.