Out of a series of 1563 consecutive patients submitted to thoracotomy for lung cancer between 1980 and 1990, 278 patients underwent a resection for a non small cell lung cancer (NSCLC) with mediastinal node metastases (N2). Selection of cases for surgery was carried out using CT from 1983 and mediastinoscopy for the patients with mediastinal lymph nodes larger than 1.5 cm from 1985: all patients with positive mediastinoscopy were excluded from thoracotomy, but 10 cases underwent a resection after neoadjuvant radio-chemotherapy. The surgical procedures were pneumonectomy (106), lobectomy (146) and atypical resection (8) with ipsilateral mediastinal lymphadenectomy. Resection was complete in 236 patients (84.8%) and incomplete in 42 patients (15.2%). Postoperative mortality was 3.2%. Almost all patients received radiotherapy after surgery. Actuarial 5-year survival was 13.7% for the entire group and 18.5% for the patients who underwent curative resection; no patients survived 5 years after palliative resection (p < 0.05). There were no differences with regard to prognosis according to the histology of the tumors and to surgical procedures. A better prognosis is associated with: completeness of resection, involvement of only one level, low T classification. Five-year survival rate of patients with metastases only in upper mediastinum was 25%; on the contrary 5-year survival rate of patients with metastases in the lymph nodes of the lower mediastinum was only 8% (p < 0.05). In our opinion better results among the patients with metastases in the upper mediastinum depends on the selection obtained with mediastinoscopy.(ABSTRACT TRUNCATED AT 250 WORDS)