PURPOSE: To evaluate the CT findings of histopathologically proven pulmonary hamartoma MATERIALS AND METHODS: CT findings of 16 patients with pulmonary hamartoma, histopatologically proven between 1990 and 1996, wereretrospectively reviewed. Diagnosis was based on thoracotomy9n=11) or fine-needle aspiration biopsy(n=5). Weanalyzed the location, margin discreteness, shape, and size of the mass, and the presence of calcification or fatdensity, as seen on CT scan. RESULTS: All 16 tumors showed a discrete and smooth margin and there was nopredilection for any specific site. They were lobulated(11/16, 69%), round(4/16, 25%) or oval(1/16, 6%) and wereless than 1cm(2/16), 1~ < 2cm(4/16), 2~ < 3cm(5/16), 3~ < 4cm(3/16) or 4~5cm(2/16) in size. Nine of 16 cases(56%)showed calcification;this was either popcorn-type(n=3), stippled(n=3), eccentric(n=2), or diffuse(n=1). Five of 16cases(31%) showed fat attenuation. CONCLUSION: On CT, pulmonary hamartomas showed a discrete margin, werelobulated (rather than round or oval) and varied in size. calcification was more common than fat density. These CTfindings may be useful for the differential diagnosis of pulmonary hamartoma.