The efficacy of radiotherapy in locally advanced unresectable non-small cell lung cancer is low. This method does not provide effective eradication of bulky disease in the thorax, neither does it prevent uncontrolled systemic disease. The addition of chemotherapy to radiation results in increased cure rate by both improving tumor control in the thorax and by eliminating or delaying the emergence of metastatic disease. The two most frequently tested strategies of combining chemotherapy and radiation include primary chemotherapy followed by radiation and concurrent application of both methods. This review provides the rationale for this strategy and presents the results of major Phase III studies. Discussed are advantages of chemoradiation, its limitations in clinical practice and prospects for the future.