Radiation therapy is the elective treatment of inoperable non small cell lung cancer, but is potentially curative only for a few of them: failures result from distant metastases and/or from progressive local disease. During the last years, following the progress in chemotherapy, combining radiation and drugs is becoming a more common approach. Nevertheless, one of the main concerns remains the potential interference between both modalities leading to an increased toxicity, which may outweigh all potential benefit. Several organs can be a target for acute or late toxicity: lung (pneumonitis and fibrosis), esophagus (acute esophagitis, stenosis), heart (pericarditis, impaired ventricular functions, heart failure, coronary stenosis), spinal cord (transient myelopathy, radiation myelitis), skin (moist desquamation, fibrosis, telangiectasia). The current published trials combining drug and radiation appear to be a rather safe approach especially when avoiding concomitant treatment. However, several points remain unsolved: the optimal combination scheme, the real risk of late damage observation including the second cancer occurrence risk. This risk is uneasy to evaluate due to the long latency period. The way of describing the late damage is crucial, seeking for a more precise system of evaluating, recording and reporting late effects, taking into account objective damage as well as the patient's symptoms. Therefore, combining drug and radiation should preferentially be performed within prospective studies, with precise evaluation procedures.