Introduction. Radiotherapy, like other oncological treatment methods, is associated with a significant deterioration in the daily functioning of patients in all spheres of life. Aim. The aim of the study was to assess the impact of radiotherapy on the quality of life of patients during breast cancer treatment. Material and methods. The research material that was used to develop the work was obtained using the research method, which is a diagnostic survey. The study included women undergoing breast cancer treatment between the ages of 18 and 70. The research was carried out from 01.09 to 30.10.2022. The paper was based on a self-survey and standardized questionnaires EORTC QLQ-C30 and EORTC QLQ-BR2 were used. Results. The assumed hypotheses were confirmed. During radiotherapy, patients indicated significant problems when performing strenuous activities. They also felt significant limitations during their work and hobbies. During radiation therapy, women experienced some problems related to cognitive functioning. Radiation therapy affected the social and emotional functioning of the patients. Radiation significantly affected the sensation of pain, shortness of breath, difficulty sleeping, lack of appetite, constipation, diarrhoea and financial problems. There were also side effects of the treatment. Conclusions. The study showed that the patients' quality of life changed during radiotherapy and significantly deteriorated cognitively, emotionally, and socially.