OBJECTIVE To investigate the effects of food hardness on chewing behavior in children compared with adults. METHODS Healthy children (3-17 years) were equally divided into five groups based on their dental eruption stages. Each participant ate soft and hard viscoelastic test food models (3 each), while the three-dimensional jaw movements and electromyographic (EMG) activity of the bilateral masseter muscles were recorded. The data from the children were compared with a control group of healthy adults (18-35 years). The data were analyzed with nonparametric tests. RESULTS There was no significant difference in the number of chewing cycles and the duration of the chewing sequence between children groups and adults. Children with primary dentition (3-5 years) showed shorter lateral jaw movement and higher muscle activity at the end of the chewing sequence, compared with adults. Further, children's age-groups (3-14 years) failed to adapt their jaw muscle activity to food hardness. However, at the late-permanent dentition stage (15-17 years), children were capable of performing adult-like chewing behavior. CONCLUSIONS Overall, it seems that children as young as 3-year-old are quite competent in performing basic chewing function similar to adults. Yet, there are differences in the anticipation or adaption of jaw muscle activity and jaw kinematics to food hardness. CONCLUSIONS The study may have clinical implication in the diagnosis and management of children with chewing impairment associated with dental malocclusions and other orofacial dysfunctions.