Abstract: Molecular imaging of breast cancer continues to rapidly expand due to improvements in both instrumentation and newer, more specific tracers.¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) is still the most widely used tumor imaging agent, but a multitude of new PET tracers are under development, many of which are aimed at targeting cellular processes that are more specific than glucose metabolism. These tracers include thymidine analogs such as ¹⁸F-fluoro-L-thymidine (FLT) that target DNA replication as a measure of cell proliferation, annexin V derivatives that evaluate apoptosis, estrogen receptor(ER)tracers such as 16α-(¹⁸F-fluoroestradiol-17β, FES), and engineered antibody fragments that directly target HER-2/neu receptors. PET-CT inline scanning was applicated more and more widely. Other new scanning devices are also being developed, including small gantry PET scanners designed specifically for breast imaging, and handheld PET probes for direct intraoperative localization of tracer-avid tumor foci.