Theories regarding children's reliability as witnesses suggest that children are more likely to confuse memories from different sources especially when the sources are highly similar. To investigate the developmental aspects of source retrieval, we measured brain electrical activity from children and adults while they retrieved content and source information. Similar brain responses among the age groups were found when participants were asked to retrieve content information. However, retrieval of source information improved with age and was accompanied by different patterns of brain potentials. The results implicate immaturity of frontal lobe structures in children's difficulty in retrieving source information.