The treatment of breast cancer requires intensive methods. Depending on the severity of the disease surgery, radiotherapy, chemotherapy, or endocrine therapy is applied. In most cases these methods are combined, thus increasing the chances of recovery, but also intensifying side effects. Until recently, physical activity was contraindicated in the treatment of malignant tumours. Currently, an increasing number of studies confirm the beneficial effect of physical activity on the physical and mental state of people after the treatment of malignant tumours. The paper presents selected studies showing the impact of physical activity on the physical fitness of women treated for breast cancer. The authors draw attention to the difficulty of comparing the results of physical activity due to the use of different questionnaires and different methods. Furthermore, the paper includes recommendations on forms of exercise indicated for cancer patients, as well as situations that require restrictions or constitute a contraindication for physical activity.