Children's long-latency auditory event-related potential (LLAEP) structure differs from that of adults. Functional significance of childhood ERP components is largely unknown. In order to look for the functional correlates in adult and children's LLAEPs, stimulus-complexity effects were investigated in 8-10-year old children. To this end, auditory ERPs to vowels, acoustically matched complex tones, and sinusoidal tones were recorded. All types of stimuli elicited P100-N250-N450 ERP complex. Differences between the sinusoidal and complex tones were confined to the P100 and N250 peaks, complex tones eliciting larger responses. Vowels elicited smaller-amplitude N250 but larger-amplitude N450 than the complex tones. Some stimulus-complexity effects observed for N250 in children corresponded to those observed for the N1 in adults, whereas the N450 peak exhibited behaviour resembling that of the adult ERP components subsequent to the N1 wave.