Accurate preoperative staging of the mediastinum is important in the treatment of non-small-cell lung cancer. Enlarged mediastinal lymph nodes on chest computed tomography are positive for malignancy on mediastinoscopy in only half of these patients. After negative mediastinoscopy, some positive nodes are found at thoracotomy. The aim of this study was to attempt to remove all lymph nodes accessible by cervical mediastinoscopic lymphadenectomy and reevaluate the same mediastinal stations at thoracotomy for missed lymph nodes. Between 1999 and 2003, 30 patients with operable non-small-cell lung cancer and enlarged mediastinal lymph nodes (>1 cm in diameter on computed tomography) that were negative on cervical mediastinoscopy underwent pulmonary resection with complete lymph node dissection. The total number of lymph nodes dissected in these 30 patients was 329 (143 at mediastinoscopy and 186 at thoracotomy); the mean numbers of nodes dissected were 4.8 at mediastinoscopy and 6.2 at thoracotomy. Ten (6.5%) residual lymph nodes were detected at thoracotomy in mediastinal stations R4, L4, and 7. The low number of missed lymph nodes demonstrates the accuracy of the technique of cervical mediastinoscopic lymphadenectomy.