The aim of this study was the comparison of basic characteristics of the P3 subcomponents elicited in passive and active versions of the auditory oddball paradigm. A 3-stimulus oddball paradigm was employed in which subjects were presented with random sequence of tones while they performed a discrimination task in visual modality with no response to the tone (passive task) or responded to an infrequently occurring target stimulus inserted into sequence of frequent standard and rare non-target stimuli (active task). Results show that the magnitude of the frontal P3 response is determined by the relative perceptual distinctiveness among stimuli. The amplitude of frontal component is larger for the stimuli more deviated from the standard in both passive and active tasks. In all cases however, a maximum over central or fronto-central scalp regions was demonstrated. Moreover, amplitude of this component was influenced by the strength of attentional focus ? a significantly larger response was obtained in the active session than in its passive counterpart. The apparent parietal P3 responses were obtained only in the active condition. The amplitude of this component is larger for the target than the non-target across all electrode sites, but both demonstrated a parietal maxima. This findings suggest that generation of early frontal P3 could be related to alerting activity of frontal cortex irrespective of stimulus context, while generation of later parietal P3 is related to temporo-parietal network activated when neuronal model of perceived stimulation and attentional trace are comparing.