We offer an illustrative case about estrogen receptor (ER) imaging (also known as 16 alpha-[F-18]fluoro-17 beta-estradiol ([F-18]-FES) PET) and the detection of metastatic lesions in the dural region. We present a case of a woman with ER-positive metastatic breast cancer and high [F-18]-FES uptake in the dural region on PET imaging, without associated clinical symptoms. These lesions were missed on [F-18]-FDG PET because of physiological [F-18]-FDG uptake in the brain. This case highlighted some difficulties in the interpretation of imaging of brain metastases and demonstrated the added value of [F-18]-FES PET imaging. [F-18]-FES PET could be used to prove the presence of ER-positive metastases in the brain.