The pathological behavior of patients with an eating disorder reflects a deficit in real-life decision-making. This function was assessed in 34 eating disorder patients and compared with that of 39 healthy volunteers using the Iowa Gambling Task. This task simulates real-life decision-making by assessing the ability to sacrifice immediate rewards in favor of long term gains. As some studies have demonstrate some relation between personality traits and decision-making functioning, the Temperament and Character Inventory-Revised, the Sensitivity to Punishment and Sensitivity to Reward Questionnaire, and the Barratt Impulsiveness Scale were also used. Eating disorder patients performed poorly in the Iowa Gambling Task compared to controls, confirming a deficit in decision-making in these patients. Regarding personality traits, impulsivity was negatively correlated with decision-making functioning in eating disorder patients. In conclusion, our results suggest a specific deficit in eating disorder patients which may be related to their pathological eating behavior. Future studies are suggested to better understand the decision-making functioning in these patients.