Radiographically occult lung carcinoma has a very good prognosis after complete surgical resection. In medically inoperable patients three-dimensional conformal radiation therapy cannot be performed, as computed tomography scan images fail to localize the disease. Presented here is an original technique of marking radiographically occult tumors by fiberoptic bronchoscopy, applied on four patients. No short-term complications were recorded. All the patients are alive, with no evidence of disease, after a mean follow-up of 15 months.