Defining high-grade glioma resectability is a challenge; and currently, it is based on anatomical imaging. However, complete removal of contrast-enhancing tumor is difficult to define in MRI. We present three cases of patients diagnosed with high-grade glioma. Brain MRI and 18F-fluorocholine PET/CT were performed before and after surgery to establish the extent of resection (EOR) and residual volume. Postoperative brain MRI and PET parameters showed discordant results in all the reported cases. PET was able to assess properly the EOR; however, the rules for the EOR establishment and its prognostic implication should be validated in prospective studies.