Many survivors of head injury suffer chronic personality changes, such as increased impulsivity and a lack of insight and poor judgment. These changes are well recognized and likely to affect the ability to make decisions. However, systematic investigations into their nature have been limited. This study aims to explore the nature of decision making in head injury survivors using a computerized task. Forty-three head injury survivors and a group of 29 matched controls completed the computerized task. The task required participants to make a probability-based choice and to further qualify this choice with an associated "bet." This betting component allows an assessment of the participant's level of confidence in the decision, via the affective evaluation of its possible consequences in terms of points won or lost. The survivors were found to be slow at making the probability- based choice. Whilst at highly favorable odds, the survivors chose the most likely option in a similar manner to the controls, they chose the most likely option less often than the controls at less favorable odds. Examination of the survivors' betting behavior revealed that they responded impulsively compared to controls. This pattern of prolonged decision making and poor quality of decisions is similar to that found in patients with orbitofrontal cortex lesions, whilst impulsive betting has been associated with abnormalities of the dopamine system. These complex deficits in decision making may contribute to difficulties with poor judgment and inhibition in head injury survivors.