FDG PET is an imaging technique used to assess regional differences in glucose metabolism. A variety of diseases, including malignancy, can show abnormal FDG uptake in bone marrow. PET/CT demonstrated non-specific uptake in the extremities of two patients with fever of unknown origin (FUO). Both patients showed focal and symmetric FDG uptake in the bone marrow of the arms and legs. Although the results of these cases were not diagnostic, the unique uptake pattern of PET/CT should be considered a non-specific reactive change as well as malignancy or other possibilities in the initial differential diagnosis.