Ionizing radiations may induce biologic responses that depend on many factors such as Physical specifications of ionizing radiation as well as biological system factors. It is shown that patients with same type of Cancer and treatment regimen may show different radiosensitivity which may be due to different specifications of their biological systems. It is revealed that many biologic factors including age, sex, smoking and existence of genetic background disease affect radiosensitivity. However, by elimination of these factors and also by similar doses of radiation, Patients may still show different biological responses such as acute and low responses. A review on recent findings about radiation modifiers in treatment of Cancer is the subject of the present article.