The central mechanisms of attention involuntary and voluntary regulation were studied in school children from the North region with the P300 (oddball task) eventrelated potential (ERP) method. ERP measurements were assessed in conjunction with behavioral tests. Our results showed different P300 waveform as well as P300 maturational changes in children in "passive" tone listening and "active" deviant tone counting task. Responses to deviant stimuli consisted of 3 dissociable components in the P300 time range: frontal-central component (Novelty P3), parietal component and an additional anterior component. Age-related reduction of P300 latency coincided with increase in information processing speed and short-time memory capability as indicated by behavioral tests. A significant negative correlation between age and P300 latency was found in central, temporal and posterior cortical areas in passive task, and all over the cortices including frontal leads in active task. The most pronounced P300 changes were found in children aged from 7 to 12. This period is suggested to be "critical" in learning skills development. Role of parietal and frontal cortex is discussed in relation to mechanisms of attention involuntary and voluntary mechanisms, as well as usefulness of P300 diagnostic is considered as to revealing of children with delayed delayed cognitive development.