Background: The extent of resection is important to improve survival in patients with a glioblastoma. The neurosurgeon's aim is to maximize the extent of resection, while preserving functional integrity. A standard to assess and compare the quality of neurosurgical care of teams is lacking. In this study we present a novel volumetric method to quantify resection residues throughout the brain for patient populations. This allows direct comparison of surgical results between care teams. Materials and Methods: All adults with a newly-diagnosed glioblastoma who had neurosurgical treatment in 2012 or 2013 in each of two tertiary referral centres for neuro-oncological care were included in this study. From each of these patient populations the outlines of preoperative tumors and postoperative residues were segmented on MRI. Tumor and residue segmentations were registered to standard space. Brain maps of tumor and residue locations were constructed for each center. Differences between these brain maps were analyzed to explore patient selection and treatment variation. Results: The study cohort consisted of 268 patients who received neurosurgery; 99 were treated by one care team, 169 by the other. Biopsies were performed in 88 patients and resective surgery in 180. The tumor localization maps confirmed established preferential locations of glioblastoma. A significant dissimilarity was noted as the patient populations of the care teams differed in tumor distribution, which may indicate differential patient referral, selection or recruitment. For patients who had resective surgery, the resection probability maps demonstrated significant differences in resected regions in the anterior internal capsule and the caudate nucleus, which may indicate treatment variation. Several arguments for these differences were considered by the care teams. Further analysis will explore whether these variations are associated with differential functional outcome or survival. Conclusions: Brain maps of tumor localization convey important information that can be used to compare neurosurgical centers in terms of patient selection. In addition, dissimilar resection probability maps may indicate treatment variations. This novel volumetric approach can provide objective arguments for discussions between care teams on the quality of neurosurgical care for patients with a glioblastoma.