BACKGROUND: An association between childhood obesity and ADHD (Attention Deficit Hyperactivity Disorder) has been recently reported. However, study on the association between childhood obesity and ADHD is scarce in Korea. This study aims to investigate whether there is any association between childhood obesity and ADH tendency in elementary school children in Korea. METHODS: The study participants involved either 5th or 6th grade students (436 students) from two elementary schools in Busan during February 2010. Children's BMI (Body Mass Index) was calculated using their height and weight measured in school while ADH tendency was assessed via a questionnaire using a standardized scale. Data were analyzed by using ANOVA and Pearson's Correlation. RESULTS: Among the subjects, 15.7% of the children was overweight and 7% obese. The average ADH tendency score among the obese group (26.1 +/- 12.85) was significantly higher than that of the normal body weight group (18.4 +/- 8.71). The ADH tendency score was positively correlated with BMI (R = 0.240, P < 0.01), gender (R = 0.248, P < 0.01), and negatively correlated with grade (R = -0.115, P < 0.05). The more obese the children were, the higher the ADH tendency score. CONCLUSION: This study reveals that ADH tendency is associated with obesity among school children. Physicians should be aware of the increased ADH tendency among obese children and should provide psychological support in treating obese children.