The neurocognitive mechanisms underlying dishonest moral decisions have yet to be fully clarified. In this talk, I will present the results of functional neuroimaging study, which focused on reward sensitivity as a potential facilitating factor of dishonest behavior. Subjects underwent functional magnetic resonance imaging (fMRI) while completing a monetary incentive delay (MID) task in which they anticipated a monetary reward, no reward, or the avoidance of monetary punishment. Individual differences in reward sensitivity were indexed by the level of fMRI BOLD signal in the nucleus accumbens during the anticipation of reward. Subjects also performed an incentivized prediction task that gave them repeated opportunities to earn money dishonestly by lying. Subjects attempted to predict the outcomes of random computerized coin-flips and were financially rewarded for accuracy. In some trials, subjects recorded their predictions in advance. In other trials, subjects were rewarded based on self-reported accuracy, allowing them to gain money dishonestly by lying about the accuracy of their predictions. Dishonest behavior was indexed by improbably high levels of self-reported accuracy. Results revealed that reward sensitivity in the nucleus accumbens, as measured using the MID task, predicted the frequency of dishonest behavior across individuals in the coin-flip prediction task. Individuals showing relatively strong nucleus accumbens responses to anticipated rewards also exhibited increased dorsolateral prefrontal activity in response to opportunities for dishonest gain. These results suggest that reward sensitivity is an important determinant of dishonest behavior.