Complex electroencephalographic (EEG), stabilographic and psychological study was executed during the number dual tasks performance--postural control and calculation in 25 healthy volunteers (age 25 ± 0.7). Successful performances of dual tasks required a high usage of cognitive resources, such as memory and attention as well as good motor command and low level of anxiety. Two EEG-markers of successful dual tasks performance were revealed. An increase of EEG coherence for long diagonal pairs of leads between frontal and parieto-occipital areas was observed. Additionally a decrease of EEG coherence for short pairs of leads was revealed. The poor performance of dual tasks was accompanied by an increase of EEG coherence between local pairs of leads for different spectral bands.