There is limited knowledge of cognitive outcome extending beyond 5 years after childhood traumatic brain injury, CTBI. The main objectives of this thesis were to investigate cognitive outcome at 6-14 years after CTBI, and to evaluate if advancements in the neurosurgical care, starting 1992, did influence long-term outcome and early epidemiology. An additional aim was to study the relationship between early brain injury parameters and early functional outcome. Study 1 evaluated cognitive progress during 14 years after CTBI, over three neuropsychological assessments in 8 patients with serious CTBI. Study 2 used patient records to investigate early epidemiology, received rehabilitation and medical follow up in two clinical cohorts, n=82 and n=46, treated neurosurgically for CTBI before and after 1992. An exploratory cluster analysis was applied to analyse the relation between early brain injury severity parameters and early functional outcome. In Study 3, participants in the two cohorts, n=18 and n=23, treated neurosurgically for CTBI before and after 1992, were subject to an extensive neuropsychological assessment, 13 and 6 years after injury, respectively. Assessment results of the two cohorts were compared with each other and with controls. Data were analysed with multivariate analyses of variance. Results and discussion. There were significant long-term cognitive deficits of similar magnitude and character in the two cohorts with CTBI, treated before and after the advancements in neurosurgical care. At 6-14 years after injury, long-term deficits in verbal intellectual and executive functions were found, and were discussed in terms of their late maturation and a decreased executive control over verbal memory-functions after CTBI. Visuospatial functions had a slightly better long-term recovery. The amount of rehabilitation received was equally low in both cohorts. The length of time spent in intensive care and the duration of care in the respirator may have a stronger relationship to early outcome than does a single measure of level of consciousness at admission. Main conclusions are that cognitive deficits are apparent at long-term follow up, 6-13 years after neurosurgically treated CTBI, even after advancements in the neurosurgical care in Sweden. Measures of verbal IQ, verbal memory and executive functions were especially low while visuospatial intellectual functions appear to have a better long-term recovery.