Diagnosis of an eating disorder (ED) has been associated with differences in cognition. Recent evidence suggests that differences may be present prior to onset. Children at familial high risk for ED show cognitive differences at ages 8-10 years. Research is required to investigate differences in cognitive development at various time points. This is the first study to investigate cognitive development in children at high risk at 18 months (Griffiths Mental Development Scale; n=982) and 4 years old (Wechsler Preschool and Primary Scale of Intelligence-Revised; n=582), in comparison with children not at risk, using a general population sample, the Avon Longitudinal Study of Parents and Children. Children of women with lifetime anorexia nervosa revealed difficulties in social understanding, visual-motor function, planning and abstract reasoning. Cognitive differences observed here have also been observed in clinical groups. This suggests difficulties may be present prior to onset, potentially affecting risk status for development of ED. Findings contribute to an understanding of aetiology, and design of prevention/intervention strategies.