Interpretation of 18F-FDG PET/CT studies in breast is challenging owing to nonspecific FDG uptake in various benign and malignant conditions. Benign conditions include breast changes in pregnancy and lactation, gynecomastia, mastitis, fat necrosis, fibroadenoma, intraductal papilloma, and atypical ductal hyperplasia. Among malignancies, invasive ductal carcinoma and invasive lobular carcinoma are common histological types of breast carcinoma. Rarely, other unusual histological types of breast carcinomas (eg, intraductal papillary carcinoma, invasive micropapillary carcinoma, medullary carcinoma, mucinous carcinoma, and metaplastic carcinoma), lymphoma, and metastasis can be the causes. Knowledge of a wide spectrum of hypermetabolic breast lesions on FDG PET/CT is essential in accurate reading of FDG PET/CT. The purpose of this atlas article is to demonstrate features of various breast lesions encountered at our institution, both benign and malignant, which can result in hypermetabolism on FDG PET/CT imaging.