A 66-year-old man who underwent an extirpation of thymoma in stage I on September 16 1997 was followed in the outpatient clinic. In October 1998, a chest CT scan revealed a 2.0 x 1.0 cm faint frosted glass like shadow in the right S9. On September 13 1999, the patient was admitted to the hospital for close examination. Two times of transbronchial lung biopsy could not offer any clear diagnosis because the lesion was present so as to encircle the central segment of the B9 gronchus. A segmental resection (S9 + 10) under thoracotomy was performed. Intraoperative frozen section diagnosis was bronchioloalveolar carcinoma (type A according to Noguchi's classification), and a resection of the remnant lower lobe and mediastinal lymph nodes dissection (ND 2 a) were added. With expected increase in frequency of detecting early pulmonary cancer's through CT, clinical cases for which we are obliged to diagnosed the disease by segmental resection may increase, if the lesion develops in the vicinity of the hilum of lung like this case.