Computerized tomography (CT) scanning provides an objective assessment of the structural damage to the brain following traumatic brain injury (TBI). We aimed to describe and quantify the relationship between CT characteristics and 6-month outcome, assessed by the Glasgow Outcome Scale (GOS). Individual patient data from the IMPACT database were available on CT classification (N = 5209), status of basal cisterns ( N = 3861), shift ( N = 4698), traumatic subarachnoid hemorrhage (tSAH) ( N = 7407), and intracranial lesions ( N = 7613). We used binary logistic and proportional odds regression for prognostic analyses. The CT classification was strongly related to outcome, with worst outcome for patients with diffuse injuries in CT class III (swelling; OR 2.50; CI 2.09-3.0) or CT class IV (shift; OR 3.03; CI 2.12-4.35). The prognosis in patients with mass lesions was better for patients with an epidural hematoma (OR 0.64; CI 0.56-0.72) and poorer for an acute subdural hematoma (OR 2.14; CI 1.87-2.45). Partial obliteration of the basal cisterns (OR 2.45; CI 1.88-3.20), tSAH (OR 2.64; CI 2.42-2.89), or midline shift (1-5 mm-OR 1.36; CI 1.09-1.68); >5 mm-OR 2.20; CI 1.64-2.96) were strongly related to poorer outcome. Discrepancies were found between the scoring of basal cisterns/shift and the CT classification, indicating observer variation. These were less marked in studies that had used a central review process. Multivariable analysis indicated that individual CT characteristics added substantially to the prognostic value of the CT classification alone. We conclude that both the CT classification and individual CT characteristics are important predictors of outcome in TBI. For clinical trials, a central review process is advocated to minimize observer variability in CT assessment.