For many years, thoracic radiotherapy had been regarded as the standard treatment for patients with unresectable locally advanced non-small cell lung cancer. However, meta-analyses show that cisplatin-containing chemoradiotherapy is significantly superior to radiotherapy alone in terms of survival. Moreover, concurrent chemoradiotherapy yields a significantly increased response rate and enhanced survival duration when compared with the sequential approach. Cisplatin-based chemotherapy with concurrent thoracic radiotherapy yields a 5-year survival rate of approximately 15% for patients with unresectable locally advanced non-small cell lung cancer. The state-of-the-art treatment for limited-stage small cell lung cancer is considered to be four cycles of combination chemotherapy with cisplatin plus etoposide combined with early concurrent twice-daily thoracic irradiation (45 Gy). If patients achieve complete remission, prophylactic cranial irradiation should be administered. A 5-year survival rate of approximately 25% is expected with the state-of-the-art treatment for limited-stage small cell lung cancer. Chemoradiotherapy is considered to be a standard treatment for both unresectable locally advanced non-small cell lung cancer and limited-stage small cell lung cancer. Several new strategies are currently being investigated to improve the survival of these patients. The incorporation of target-based drugs such as gefitinib is considered to be the most promising strategy for unresectable locally advanced non-small cell lung cancer. The incorporation of irinotecan is also a promising strategy to improve the survival of patients with limited-stage small cell lung cancer. The Japan Clinical Oncology Group is conducting clinical trials to develop new treatment strategies for both unresectable locally advanced non-small cell lung cancer and limited-stage small cell lung cancer.