Positron emission tomography (PET) has revolutionized the diagnostic opportunities of malignances, however, it has still a controversial role at some conditions in the management of breast cancer. The article compares PET alone and PET/CT. We review the latest trends of using PET or PET/CT for diagnosis, staging, evaluation of the primary tumor and regional lymph node status, as well as early detection of recurrence and distant lesions. PET/CT provides new methods of assessment of early chemo/endocrine therapy response of locally advanced breast cancer. We discuss the development of new radiotracers and their value in predicting treatment response, identifying tumor subtypes and finding new therapeutic targets by them.