Stage III includes a large variety of clinical situations from chest wall invasion together with intralobar lymph node metastasis to any size of a lung cancer in combination with mediastinal lymph node involvement (N2/N3). Furthermore, the prognosis of patients with lymph node metastasis depends largely on the extent of the disease, which may range from micro-metastasis occasionally found during surgery to bulky and/or multilevel involvement of the mediastinum or extracapsular infiltration. Not surprising the optimal treatment including the role of surgery for stage IIIA (N2) and stage IIIB (T4/N3) non-small cell lung cancer is discussed controversially. Adequate analysis of the clinical stage is key to select the best treatment. In general, patients benefit from surgery, when a radical resection can be achieved with a low morbidity and mortality. A multidisciplinary approach is indicated in most patients, which present with stage III disease at diagnosis. Preferentially patients should be treated in study protocols whenever they are available. Radical surgery including chest wall resection may result in a 5-year survival rate of up to 50% in T3N1 disease. Adjuvant chemotherapy is recommended and radiotherapy is reserved for cases with unclear resection margins. Clinical trials of preoperatively proven N2 patients could show a better outcome when downstaging is achieved after neoadjuvant chemo- or chemoradiotherapy prior to surgery. Patients who may need a pneumonectomy should be selected with caution since some centers experience a high perioperative mortality rate. If unforeseen N2 disease is found during surgery, an adjuvant therapy is recommended. Patients with T4 tumors (infiltration of great vessels, trachea, esophagus, vertebral bodies, etc.) show an increasing 5-year survival from 15 to 35% after radical resection with acceptable perioperative mortality if treated in experienced centers. In stage III non-small cell lung cancer, surgery should be performed within a multimodality approach. Surgery should be recommended when resection is radical including systematic lymph node dissection and mortality and morbidity are low.