Infantile fibrosarcoma (IFS)is an uncommon tumor and predominantly found in children less than 2 years of age. It is a low-grade non-rhabdomyosarcoma soft tissue sarcoma (NRSTS) and usually presents as a solitary, non-tender mass in the soft tissue layer of the extremities. F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT)is a well-established modality in the assessment of malignancies including initial detecting location, staging, restaging and therapeutic monitoring. Reports of F-18 FDG PET/CT studies in children patients with IFS, however, are extremely rare. We describe an 8-month-old male infant diagnosed with IFS in the right calf. Eleven months after a surgical resetion, he was detected a local reurrent tumor at the same position by F-18 FDG PET/CT.The roles of F-18 FDG PET/CT in the detection and mangement of IFS will be discussed.