Background: The Pediatric Emergency Care Applied Research Network (PECARN) decision rule demonstrates high sensitivity for identifying children at low risk for clinically important traumatic brain injury (ciTBI). As with the PECARN rule, the Israeli Decision Algorithm for Identifying TBI in Children (IDITBIC) recommends proceeding directly to computed tomography (CT) in children with Glasgow Coma Score (GCS) <15. The aim was to assess the diagnostic accuracy of two clinical rules that assign children with GCS <15 at presentation directly to CT. Materials and methods: Accuracy analysis for detecting ciTBI was performed on a multicenter cohort of children used in the Australasian Pediatric Head Injury Rules Study. Results: The external cohort included 18,913 children; 1691 (8.9%) had CT scan, 160 had ciTBI, and 24 (0.13%) had neurosurgery. Applying IDITBIC and PECARN rules would have missed 11 and 1 ciTBI patients; respectively. All patients with missed injuries were classified as such based on a hospital stay of >2 d. None of these patients died, needed neurosurgery, or required ventilatory support. In children aged <2 y, sensitivity, specificity, positive predictive value and negative predictive value of IDITBIC and PECARN rule were 95.2%, 79.5%, 3.8%, and 99.9% and 100.0%, 59.1%, 2.0%, and 100.0%, respectively. In children ≥2 y, sensitivity, specificity, positive predictive value and negative predictive value of IDITBIC and PECARN rule were 92.4%, 75.3%, 3.1%, and 99.9% and 99.2%, 52.9%, 1.7%, and 100.0%, respectively. Conclusions: The two decision rules demonstrated high accuracy in identifying ciTBI. As a screening tool, the PECARN rule outperformed IDITBIC. The findings suggest that clinicians should strongly consider directing children with GCS <15 at presentation to CT scan.