OBJECTIVES: Complicated mild traumatic brain injury (mTBI) or cmTBI is based on the presence of visibly identifiable brain pathology on the day-of-injury computed tomography (CT) scan. In a paediatric sample the relation of DOI CT to late MRI findings and neuropsychological outcome was examined. METHODS: MRI (>12 months) was obtained in paediatric cmTBI patients and a sample of orthopaedically injured (OI) children. Those children with positive imaging findings (MRI+) were quantitatively compared to those without (MRI-) or with the OI sample. Groups were also compared in neurocognitive outcome from WASI sub-tests and the WISC-IV Processing Speed Index (PSI), along with the Test of Everyday Attention for Children (TEA-Ch) and a parent-rated behavioural functioning measure (ABAS-II). RESULTS: Despite the MRI+ group having significantly more DOI CT findings than the MRI- group, no quantitative differences were found. WASI Vocabulary and Matrix Reasoning scores were significantly lower, but not PSI, TEA-Ch or ABAS-II scores. MRI+ and MRI- groups did not differ on these measures. CONCLUSIONS: Heterogeneity in the occurrence of MRI-identified focal pathology was not associated with uniform changes in quantitative analyses of brain structure in cmTBI. Increased number of DOI CT abnormalities was associated with lowered neuropsychological performance.