Numerous primary and metastatic osseous lesions and incidental osseous findings are encountered at fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT. These lesions show varying degrees of FDG uptake. Malignancies are generally more FDG avid than are benign lesions, but many exceptions exist. Although aggressive lesions tend to be more FDG avid than nonaggressive lesions, this concept holds true particularly for lesions of the same histologic subtype. In addition, some benign osseous processes such as Paget disease have variable degrees of FDG avidity on the basis of disease metabolic activity. This creates a diagnostic dilemma for radiologists and clinicians, especially in patients with known malignancies, and can result in unnecessary diagnostic imaging or interventions for incidental osseous lesions. Evaluation of morphologic CT characteristics of osseous lesions at FDG PET/CT can be a valuable adjunct to metabolic analysis to further characterize lesions, enhance diagnostic and staging accuracy, and avoid unnecessary invasive biopsy procedures. The authors review the common primary and metastatic bone lesions at FDG PET/CT, with an emphasis on morphologic CT assessment of lesions to help narrow the differential diagnosis. Imaging manifestations of common incidental nonneoplastic bone lesions at FDG PET/CT are discussed to provide information on differentiation of these lesions from osseous neoplasms. The guidelines of the National Comprehensive Cancer Network (NCCN) for common primary osseous malignancies are also summarized. Online supplemental material is available for this article. ©RSNA, 2021.