While reversible cases of dementia are rare once detected, the patient may benefit from treatment. This paper examines the cost-effectiveness of computerized tomography (CT) scanning as a screening test for potentially reversible dementia. A systematic review was carried out to identify the proportion of patients with dementia above and below the age of 65 years with a theoretically treatable condition and the proportion of these patients who would benefit from neurosurgery. Information was combined with epidemiological and financial data relating to Scotland to model the costs and benefits of implementing a national screening program. Subdural hematoma, normal pressure hydrocephalus, and brain tumours are rare conditions treatable by neurosurgery. A scanning and treatment program for Scotland would cost £4.6 million per annum. Of 531 reversible cases detected, 136 would benefit from neurosurgery, 369 would not benefit, and 26 would die as a result of surgery. Treating normal pressure hydrocephalus reduces overall quality-adjusted survival. The most cost effective screening strategy is to scan all patients but treat only subdural hematomas, gaining 178 quality-adjusted life-years (QALYs) at a cost of £14,171 per QALY for patients aged 65 at the time of the scan. The corresponding figures for patients above and below 65 years are £9,000 and £23,000, respectively. CT scanning appears cost-effective in dementia patients under 65 years. It should be undertaken selectively in more elderly patients. Surgical treatment of normal pressure hydrocephalus may reduce quality adjusted survival and should only be undertaken within clinical trials.