The purpose of this study was to evaluate foot arch types of obese children and adolescents aged 9-16.5 years using both indirect and direct measures. Fifty-eight obese children/adolescents attending the paediatric endocrinology unit of the University Hospital "Lozano Blesa" in Zaragoza were selected as experimental subjects. Fifty-eight gender and age matched, normal-weight children/adolescents were selected as control subjects. To assess the medial longitudinal arch (MLA) height, which is used as a main reference for the diagnosis of flatfoot, footprints from both feet were collected (in both groups) and lateral weight-bearing radiographs of both feet were taken (of 49 of the 58 obese children). Footprint angle (FA) and the Chippaux-Smirak index (CSI) were calculated from the footprints. Talus-first metatarsal (TFMA) and calcaneal inclination angles (CIA) were obtained from lateral feet radiographs. In the normal-weight group, mean values of FA and CSI indicated a normal MLA. In the obese group, morphological flatfoot was identified. Comparison between both groups, by side and gender, showed a decrease of FA (p<0.001) and an increase of CSI (p<0.001) in obese subjects. Mean values of TFMA and CIA in the obese group indicated a lowering of the MLA. Obese children/adolescents between 9 and 16.5 years of age had significantly lower values of FA and higher CSI, related to a lower MLA. Radiographic parameters supported these findings and mean values were associated with a fall of this arch.