The pleomorphic xanthoastrocytoma is generally considered a low-grade neoplasm with favorable prognosis. These tumors, however, can demonstrate primary anaplastic features, undergo malignant transformation, disseminate, or progress with poor outcome. Currently, there are no histologic or clinical features that reliably predict recurrent tumor or tumor progression. We report three children with confirmed pleomorphic xanthoastrocytoma who were studied with positron emission tomography (PET) using [18F]fluorodeoxyglucose (FDG) coregistered with magnetic resonance imaging. One patient had decreased FDG metabolism and, despite a gross total resection and benign pathology, had early local recurrence. Subsequent to a second surgical resection and radiation therapy, he has remained stable for 8 years. One patient with significant FDG uptake had gross total resection of an anaplastic pleomorphic xanthoastrocytoma. Follow-up FDG studies showed no abnormal metabolic activity, and he has been stable without adjuvant treatment for 5 years. The last patient had intermediate FDG uptake and a moderate-grade pleomorphic xanthoastrocytoma by histopathology. She showed early tumor progression with spinal metastases. Following a near-total resection of the recurrent intracranial lesion and neuroaxis radiation, she has been stable for 4 years. Although there are still no reliable prognostic indicators for pleomorphic xanthoastrocytoma, PET with FDG correlates with histopathology, and increased uptake may be a marker for more malignant or aggressive tumors. The extent of surgical resection in regard to prognosis in our limited study is unclear but appears helpful in the anaplastic pleomorphic xanthoastrocytoma case. Adjuvant radiation therapy also may benefit certain patients. Further PET studies are warranted in this group of tumors.