A fibrolipomatous hamartoma of the lung in a 57-year-old Japanese man is reported. Computed tomography revealed an abnormal mass with fatty and soft tissue densities in the upper portion of the right lung, indicating a liposarcoma. Upon resection, the tumor was found to consist of a 7.5 x 4.0 cm soft, yellowish mass continuous with a 3.0 x 1.5 cm polyp. The tumor was composed primarily of mature fibro-adipose tissue with some glandular and cartilaginous components, which identified it as a fibrolipomatous hamartoma. Follow-up studies of the patient for two years after surgery found no sign of malignancy. Thus, lipomatous or fibrolipomatous hamartoma should be considered as a possible diagnosis whenever atypical lipomatous lung tumors are encountered.