Purpose Intramedullary (IM) nailing and plating are recognised fixation methods for both-bone midshaft forearm fractures. Although both methods are effective, IM nailing has recently been the accepted operative treatment for the paediatric population. The aim of the study was to compare the differences in the radiographic and functional outcomes of an age-and sex-matched cohort of children following treatment by IM fixation or plate fixation with screws for an unstable both-bone diaphyseal fracture. Methods A retrospective study was conducted and 17 age-and sex-matched pairs of patients returned for a research review clinic. The average age of our patients was 11.6 years at follow up, with 11 boys and six girls in each group. The mean follow up was similar in both groups (IM 31.5 months, plating 31.8 months). Results Plating and IM nailing result in good or excellent functional and radiological outcomes. Radiographs at the review clinic showed complete healing in the plating group, with reconstitution of the radial bow. Three patients in the IM group did not regain the natural radial bow radiographically. There were no significant differences between both groups for maximum radial bow and its location (P [ 0.05). However, the maximum radial bow was significantly different from normative values in both groups (P = 0.003 plate, P = 0.005 IM). No non-union or malunion was observed. There were no significant differences in the loss of forearm motion and grip strength between both groups. There was no difference in the Pediatric Orthopaedic Society of North America (POSNA) scores between both groups. The plating group had a significantly worse Manchester scar score than the IM group (P = 0.012). One major complication was observed in each group: osteomyelitis for IM fixation and ulnar never palsy for plating. Conclusion Our study suggests that functional outcome is likely to be equivalent, regardless of which method of internal fixation is used.