Background: Various functional asymmetries detected by different neurophysiological and neuroimaging methods have been reported in the literature on the Attention Deficit Hyperactivity Disorder (ADHD), some of them pointing to the right hemisphere activity. In our attempt to discriminate the ADHD patients from normal subjects by hierarchical clustering of behavioural, psychological and event related potential (ERP) variables, the late P3 component of potentials from the right central region (C4) proved to be one of the most informative parameters (in preparation for publication). Here, we have studied the differences in ERPs between the left (C3) and right (C4) central leads and relation of this asymmetry to ADHD diagnosed using DSM. Methods: 16 typically developing (TD) boys and 16 boys diagnosed with ADHD according to DSM-IV-TR, aged 10-13 years, were examined by the Attentional Network Test (ANT), with simultaneous recording of the respective ERPs. The intergroup differences in the ERP amplitude parameters in the left (C3) and right (C4) central channels and in the difference in these parameters between the two channels (C3 minus C4) were accessed. These characteristics were compared to the subjects' DSM scores and ANT performance. Results: The target-related potentials late characteristics from the C4 showed significant difference between the groups, while no difference was observed for the C3. Only in the ADHD patients, both the left and right late target ERP characteristics correlated with the reaction time, while the DSM scores did not show any correlations in both groups. The difference between ERPs of the C3 and C4 channels inside the interval of 40-290 ms after target onset was negative in the ADHD group (C3 < C4) and positive in the control group (C3 > C4). This asymmetry correlated with DSM scores, mainly to hyperactive (ADHD > control) and impulsive (control > ADHD) criteria. Conclusion: In ADHD patients, the results suggest ERP pattern of right-side functional predominance in the motor control, which correlates to DSM scores, mainly to hyperactive and impulsive criteria.