INTRODUCTION: Surgical volume has been established as an important determinant of patient outcomes, with progressive regionalization and subspecialization of care. METHODS: We identified patients 0-20 years of age who underwent neurosurgical treatment for 1 of 11 conditions in the Kids’ Inpatient Database (KID), 2003-2009: malignant brain tumor, adolescent idiopathic scoliosis (AIS), tethered cord, Chiari malformation, craniosynostosis, traumatic brain injury (TBI), traumatic spinal injury, unruptured intracranial aneurysm, hydrocephalus, peripheral nerve injury, and epilepsy. High-volume (HV) surgeons/hospitals were those in the top tertile of annual case volume. We used multivariable two-level mixed-effects logistic regression analyses to account for clustering of patients within surgeons and clustering of surgeons within hospitals. RESULTS: Overall, 40,973 patients met inclusion criteria. Patients were more likely to be treated by a HV surgeon if they were at a HV hospital (range, 51.4% for peripheral nerve repair to 75.6% for aneurysm) for all conditions except for spinal injury (34.8%). There was reduced risk of complications for HV surgeons in tethered cord, TBI, AIS, and aneurysm (all p<0.05). Adjusted for hospital volume, the effect of HV surgeons was maintained only for TBI (OR=0.81, p=0.026). HV hospitals accounted for 42% of the HV surgeon effect for tethered cord, whereas HV surgeons accounted for 94% of the HV hospital effect for aneurysm. Adjusted for hospital volume, HV surgeons had lower length of stay (LOS) for tethered cord (OR=0.31, p=0.010), nerve injury (OR=0.44, p=0.004), hydrocephalus (OR=0.60, p<0.001), and AIS (OR=0.48, p<0.001). HV hospitals accounted for 60% of the effect of HV surgeons on LOS in tumor, whereas HV surgeons accounted for 88% of the effect of HV hospitals in tethered cord, 62% in hydrocephalus, and 31% in aneurysm. Adjusted for hospital volume, HV surgeons had reduced adverse discharge for craniosynostosis (OR=0.12, p=0.005) and hydrocephalus (OR=0.52, p<0.001). HV surgeons accounted for 89% of the effect of HV hospitals in craniosynostosis, and 26% in hydrocephalus. CONCLUSION: Although surgeon and hospital volume are sometimes used interchangeably, the two may have different effects on outcomes in pediatric neurosurgery, with one at times explaining variation in the other.