The aims of the present study were to determine the rate of misinterpretation of non-contrast cranial CT scans by emergency specialists and trainees compared with specialist radiologists, and the proportion of misinterpretations that is consequential. A 12-month prospective blinded cohort study was performed. One-hundred and ninety of 1,282 scans (14.8%) were misinterpreted, and 78 of these (41.1%) were of potential or actual consequence. We conclude that the performance of senior emergency department staff in non-contrast cranial CT interpretation is no better than moderately good, and a large proportion of misinterpretations are of potential or actual clinical consequence.