BACKGROUND: Studies have shown increased bilateral activation in the prefrontal cortex when normal individuals lie, but there have been no structural imaging studies of deceitful individuals. AIMS: To assess whether deceitful individuals show structural abnormalities in prefrontal grey and white matter volume. METHOD: Prefrontal grey and white matter volumes were assessed using structural magnetic resonance imaging in 12 individuals who pathologically lie, cheat and deceive ('liars'),16 antisocial controls and 21 normal controls. RESULTS: Liars showed a 22-26% increase in prefrontal white matter and a 36-42% reduction in prefrontal grey/white ratios compared with both antisocial controls and normal controls. CONCLUSIONS: These findings provide the first evidence of a structural brain deficitinliars, they implicate the prefrontal cortex as an important (but not sole) component in the neural circuitry underlying lying and provide an initial neurobiological correlate of a deceitful personality.