The use of positron emission tomography with computed tomography (PET/CT) for adult cancer patients is widespread, however, its use in pediatric patients is limited by fear of radiation, monetary cost and lack of awareness of its greater sensitivity in the evaluation of some types of tumors. Ewing's sarcoma is one of the primary pediatric malignancies in which PET/CT with 18F-labeled fluorodeoxyglucose (18F-FDG) has demonstrated greater sensitivity in the evaluation of bone metastases compared to scintigraphy, as well as in the evaluation of treatment response. We report a 13 years old female consulting for retrosternal pain. A chest CT scan showed an infiltrating mass originating in the sternum. A biopsy confirmed the presence of an Ewing sarcoma. The tumor was staged with PET/CT which showed multiple bone lesions not visible in previous studies.