The aim of this study was to investigate the relationship between vitamin D levels and cognition, both executive and nonexecutive functions, in men incarcerated in a Norwegian prison. Participants were divided into high vitamin D and low vitamin D groups based on established criteria (high level > or = 50 nmol/L; low level < 50 nmol/L). The mean vitamin D concentration was 69 (SD = 12) and 38 (SD = 9) nmol/L in the high-level group (n = 14) and the low level group (n = 11), respectively. Results revealed that the high vitamin D group had significantly more correct responses than the low vitamin D group on the executive function task. There was no difference between the groups on the nonexecutive function task. The reaction time data indicated that the high levels of correct responses in the high vitamin D group on the executive function tasks were not due to a speed-accuracy trade-off.