Abstract Background: Breast cancer is the most common cancer and the second leading cause of cancer mortality in women. Accurate diagnosis and staging are essential for the selection of the most appropriate therapeutic strategy and major deter-minants of patient prognosis and survival. Aim of Study: The purpose of our study is to evaluate the potential role of 18F-FDG PET/CT in monitoring treatment of breast cancer and assessment of recurrence after surgical or systemic treatment. Patients and Methods: This study is retrospective study, was conducted on (25) female patients over a period of 6 months between 2018 and 2019. Their ages ranged from 34 to 78 years with mean age of 52 years, all patients have positive history of breast cancer treatment. Those patients were referred to the Radio Diagnosis Department & Nuclear Medicine Department in Ain Shams University. Results: FDG-PET-CT is the investigation of choice for post-treatment follow-up of breast cancer. It has a great role in detection of newly developed lesions and detection of the disease progression. Conclusion: FDG-PET-CT is highly useful for monitoring response to therapeutic interventions. This technique can identify response to therapy earlier than any other imaging method currently available which greatly improves patient management by allowing termination of ineffective and toxic therapies. PET-CT proved to be helpful in the evaluation of anatomic regions that have been previously treated by surgery or radiation in which the discrimination between post-treatment scar and recurrent tumor can be problematic.