Background:Childhood obesity is a major health problem. An association between children's body mass index (BMI) and overeating has been established, but mechanisms leading to overeating are poorly understood. The personality characteristics impulsivity and reward responsiveness may be involved in the tendency to overeat. Impulsivity might relate to overeating through poor inhibition of food intake; reward responsiveness through the rewarding value of food.Objective:This study aimed to reveal the relationships between impulsivity, reward responsiveness, overeating and BMI in a sample of 346 Dutch children aged 6-13 years. The BMI distribution in the sample was representative of the BMI distribution in the Dutch pediatric population.Methods:Impulsivity and reward responsiveness were measured with the Dutch version of the parent-report Sensitivity to Punishment and Sensitivity to Reward Questionnaire for children. Overeating was assessed with the Dutch translation of the parent-report Children's Eating Behaviour Questionnaire.Results:Overeating, impulsivity and reward responsiveness were significantly associated with childhood BMI. Mediation analysis revealed that impulsivity and reward responsiveness equally and significantly predicted BMI indirectly through overeating.Conclusions:The personality characteristics impulsivity and reward responsiveness predict childhood BMI indirectly through overeating. This suggests that these personality characteristics are risk factors for obesity. © 2011 Macmillan Publishers Limited All rights reserved.