Purpose: The purpose of this master's thesis is to utilize basic data in order to improve the quality of life of cancer patients who received radiation therapy after analysing related factors that influence patient's quality of life and obtaining information about physical, mental problems of patients. Materials and Methods: By using a structured questionnaire about various characteristics and forms of support, I carried out a survey targeting 107 patients that experienced radiation therapy at a university hospital in the Daejeon metropolitan area from July 15 to August 15, 2010 and analysed the factors influencing quality of life. Results: In case of pain due to disease, 65.15 and painless 81.87 showed a high grade quality of life. As body weight decreases, the quality of life become lower. When the grade of quality of life according to economic characteristics was compared, all items except treatment period showed a difference (P=0.000). When the score of social support, family support, medical support and self-esteem was low, the mark of quality of life showed respectively 61.71, 68.77, 71.31, and 69.39 on the basis of 128 points. When the score of support form was high, the mark of quality of life showed 90.47, 83.29, 90.40, and 90.36 (P<0.05). When analyzing the correlation between social support, family support, medical support and self-esteem and the degree of quality of life, social support was 0.768, family support 0.596, medical support 0.434, self-esteem 0.516. They indicated the correlation of meaningful quantity statistically (P<0.01). The factors that improved the quality of life were married state, having a job and painless status. As monthly income increases, the quality of life was also much improved (P<0.05). Among the factors related to quality of life, social support and medical support and higher self-esteem scores of the quality of life score increased 0.979 point, 0.508 points and 1.667 point, respectively. Conclusion: In conclusion, the quality of life of cancer patients that received radiation treatment is related to social support, medical support and self esteem. Self-esteem is an important factor that influenced quality of life, so if government offers works that doesn't affect patient's health, they are a useful method that maximize self-esteem and lessen their financial burden at the same time. Along with these policies, the developments of the attention of medical and the program for cancer patient's family are needed for the purpose of improving quality of life of cancer patients. Lastly, medical team, patients and family have to cooperate in harmony to overcome difficulties of cancer patients.