Age-dependent differences in cranial bone development, cerebral vascular physiology and neurological lesions distinguish neonates, infants and children from their adult counterparts. In particular, the central nervous system (CNS) undergoes a tremendous amount of structural and physiological change during the first 2 years of life. This chapter highlights these age-dependent differences and their effect on the perioperative management of the paediatric neurosurgical patient. Children in this age group can present with a wide variety of pathologies requiring surgical intervention including trauma, congenital abnormalities such as craniosynostosis, hydrocephalus, intracranial tumours, intracranial vascular lesions and seizure disorders. Age-dependent differences in cerebrovascular physiology have a significant impact on the perioperative management of neurosurgical patients. Given the systemic effects of general anaesthesia and the physiological stress of surgery, an organ system-based approach is optimal for anticipating potential physiological derangements and coexisting disease states that may increase the risk of perioperative complications.