Among a total of 114 cases of resected lung adenocarcinoma that were examined by sputum cytologic study before bronchoscopy, 17 were sputum cytology-positive, but had no abnormal bronchoscopic findings. In most of these cases, the reason for detection was sputum and bloody sputum (58.8 percent). Pathologically, many cases were classified as stage III A or more (82.4 percent) due to mediastinal lymph node metastases. More than 70 percent of the cases showed vascular invasion. The proportion of well-differentiated cases was also high (52.9 percent). The prognosis of these cases was worse than sputum cytology-negative adenocarcinoma without abnormal bronchoscopic findings and better than sputum cytology-positive adenocarcinoma with abnormal bronchoscopic findings. There was no significant difference between these cases and sputum cytology-negative adenocarcinoma with abnormal bronchoscopic findings. Combined with the bronchoscopic findings, sputum cytologic study is useful for preoperative evaluation of lymph node metastasis and prognosis. This combined approach can provide information necessary to perform sufficient dissection of mediastinal lymph nodes and proper adjuvant therapy in sputum cytology-positive adenocarcinoma cases, even though there are no abnormal bronchoscopic findings.