Recently, a number of non- targeted effects associated with radiation exposure have been identified; including bystander effects, abscopal effects, transgenerational effects and effects in multi-organism levels. One of the important effects, the bystander effect describe the situation where the radiation induces the cell or organism to send a damage to signal other cells and the responses involve apoptosis, genetic instability, mutation and induction of stress and adaptive pathways. Consequently, the bystander and other non-targeted effects have several important implications for radiation protection, radiotherapy and diagnostic radiology. Here, I will give a brief overview of a hybrid multiscale mathematical model to study the role of bystander effects in clinical radiotherapy and radiation protection.