The objective of this study was to investigate differences in measures of intelligence and personality between obese and normal-weight children. The Wechsler Intelligence Scale (IQ) for Children (revised) and the Eysenck Personality Questionnaire (EPQ) were administered to 102 children with simple obesity and their controls in a case-controlled design. The mean age of the children was 9.8 years and they all attended primary school in Nanjing, PRC. It was found that children in the severe obesity category (> 50% overweight) had a significantly lower performance IQ score than the controls, and a significantly higher EPQ psychoticism score. These differences were not observed in children with milder degrees of obesity.