PURPOSE: To evaluate the CT findings of focal organizing pneumonia and to correlate them with pathologic findings to help differentiating from lung cancer. MATERIALS AND METHODS: We evaluated radiologic and pathologic findings of five patients with solitary pulmonary nodule which were confirmed as focal organizing pneumonia pathologically. RESULTS: On CT scan, focal organizing pneumonia had irregular margin contacting the pleura in all five cases. The shape of the nodules were spherical to wedge or elliptical and the size from 3.5cm to 5.5cm (average 4.2cm) in largest diameter. On postcontrast CT scan, all nodules showed enhancement and four cases showed central low density components. Two nodules contained air within the nodule. In four cases, pleural changes such as effusion and/or focal thickening were noted. No lymphadenopathy was found in all cases. Pathologically, the enhancing portion on CT showed findings of organizing pneumonia such as granulation tissue with fibroblast proliferation in alveolar space and interstitial thickening. The central low density areas on CT were due to ischemic necrosis, abscess and exudate, transudate and infiltration of foamy histiocyte. CONCLUSION: The possibility of focal organizing pneumonia should be considered when peripherally located solitary pulmonary nodule had enhancing component with no combined lymphadenopathy on CT scan.