Abstract: Objective : To assess the prevalence of late pulmonary injury in breast cancer patients treated by postoperation radiotherapy and to identify its potential predictive factors. Methods Seventy-four radical mastectomy patients were examined prior to and more than 12 months after radiotherapy, its median was 33.6 months. Study the crude rate of late pulmonary injury by LENT-SOMA scales and its potential predictive factors by binary logistic regression of the multivariate analysis. Results : The subjective complains and objective signs in chest films of late pulmonary injury were found in 16.2% and 37.8% patients respectively. Multivariate analysis revealed that the risk of late pulmonary injury was significantly increased in the elder patients (P=0.034) and non-smokers (P=0.046), whereas more than 6 cycles chemotherapy given after radiotherapy (P=0.022). Conclusion : The late pulmonary injury is one of the familiar complications after radiotherapy for radical mastectomy, some clinical factors are associated with the increasing incidence of this disease.