Children undergoing either posterior spinal fusion (PSF) or index insertion of growing rods for neuromuscular or genetic/syndromic scoliosis may require post-operative care on the paediatric intensive care unit (PICU). Demands on this limited resource result in frequent bed shortage related cancellations. In response, an ad-hoc or 'pop-up' ward-based high-dependency unit (POPUP-HDU) was developed. This converts a ward bed to POP-HDUbed for the required time. This study assesses the safety and efficacy of postoperative management that utilises POPUP-HDU as an alternative to a PICU bed. Retrospective review of 111 consecutive children undergoing posterior surgery for scoliosis between June 2016 and April 2023. The inclusion criteria included a diagnosis of genetic/syndromic or neuromuscular scoliosis; PSF or primary insertion of distraction-based growth rods and requirement for postoperative care in a PICU. We excluded those children that were mandated to go to PICU post-operatively for any reason by the anaesthetic team. 49 patients (mean age 13.0years) were managed on PICU, and 62 (mean age 11.4years) on POPUP-HDU. The groups were matched with respect to body weight, curve magnitude, operative duration, type of fusion procedure performed, the presence of cardiac malformations, the use of home breathing support, the number of operated levels, pelvic instrumentation and intraoperative blood loss. 8 patients in the PICU, and 16 in the POP-HDU groups were readmitted back to PICU following step-down to the hospital ward (p = 0.27). The median PICU length of stay was 1day in the PICU group and less than a day in POPUP-HDU (for those that needed to be subsequently admitted to PICU). The median total length of hospital stay was 10days in the PICU group, and 8days in POPUP-HDU (p < 0.05). 14 patients developed medical complications in the PICU group, compared to 19 in POPUP-HDU. There were no bedshortage cancellations in POPUP-HDU, compared to 23 in PICU. For children with neuromuscular, genetic or syndromic scoliosis undergoing PSF or growth rods that are not deemed suitable for immediate ward-level post-operative care, POPUP-HDU provided a safe alternative to PICU for appropriate patients and was associated with shorter hospital stay and fewer cancellations for lack of PICU beds. Therapeutic Level III.