Purpose: Breast cancer is the most common among women worldwide, with one in eight women receiving this diagnosis in their lifetime. The National Comprehensive Cancer Network (NCNN) recommends receptor type testing for all breast cancer patients, which helps predict outcomes and guide treatment decisions. Breast cancer has three subtypes: hormone receptor-positive, HER2positive, and triple-negative breast cancer, depending on the expression of hormone receptor and HER2. The purpose of this study is to introduce a general understanding and usefulness of ¹⁸F-fluoroestradiol(FES) PET/CT imaging, and to investigate the SUV_max value of ¹⁸F-FES and ¹⁸F-FDG PET/CT Images. Materials and Methods: Summarizing of approval process by Korea Food and Drug Administration(KFDA) and national insurance benefits status of ¹⁸F-fluoroestradiol(FES) in Korea. To confirm the usefulness of ¹⁸F-FES PET/CT Scan, We analyzed the latest meta-analysis papers, and a paired-sample t-test(wilcoxon signed -rank test) was performed on SUVmax value measurements for 41 patients who underwent both ¹⁸F-FES PET/CT and ¹⁸F-FDG PET/CT within a month interval from Jan. 2022 to Dec. 2023. Results: ¹⁸F-fluoroestradiol(FES) was approved by KFDA in November 2019, and national insurance benefits were garneted by government in December 2020. Our study reveal that irrespective of the lesion’s anatomical site, the 18F-FES SUVmax exhibited an average of 7.8±5.9, while the 18F-FDG SUV_max demonstrated an average of 6.3±3.3. Considering the location of the lesions within the breast only, the ¹⁸F-FES SUVmax average at 7.1±5.4, with the 18F-FDG SUVmax average at 6.2±3.5. Conversely, lesions were located outside the breast an average 18F-FES SUVmax of 8.9±6.6 and an average 18F-FDG SUVmax of 6.4±3.2. Conclusions: We can find that, there was no significant difference on SUVmax value between ¹⁸F- FES and 18F-FDG PET/CT images. However, approximately 70% of breast cancer patients are diagnosed with estrogen receptor-positive breast cancer in Korea, therefore considering the importance of hormone therapy in recurred or metastatic breast cancer treatment. ¹⁸F-FES PET/CT scan is very useful clinical implementation, when evaluating breast cancer hormone receptors through the imaging, Especially, the patients who tumor biopsy is difficult or impossible conditions.