Sex differences in treatment response have been observed in overweight children. The present study therefore investigated differences in 52 boys and girls before treatment, with respect to laboratory eating characteristics, measured with a universal eating monitor. Differences were obtained for average eating rate (p<0.01), frequency of spoonfuls (p<0.01), and a trend for differences was seen for initial eating rate (p<0.10). The results point to the necessity of specific treatment elements for boys to modify their unfavourable microstructure of intake.