In neurophysiology the concept of lateralization of brain hemisphere functions is related to the existence of differences in their functioning. The aim of the research was to determine for the right-handed females whether there is a connection between the degree of lateralization of brain hemispheres and the variables of cognitive potential P300 (latency and amplitude). In 30 study participated 70 girls, age 20-23 years. In the first group where 29 strong expressed right-hand girls, in the second group 30 moderately expressed right hand girls, and in the third group 11 right-hand learned girls. The reserch workers were using the "oddball" paradigm with two tones: "standard" (90dB 1000Hz) and "expected-target" (90dB 2000Hz) for the registration of the P300 potential. The tones were binauraly presented in irregular intervals and irregular order. P300 evoked potentials were registered above Fz and Cz area. Results showed the cognitive P300 wave latency to be significantly shorter when responding with dominant hand in first group. P300 wave latency in girls from second group was a shorter with engagement of the right hand. Cognitive P300 potentials above the FZ and Cz regions àt the first group have a significantly shorter latency compared to the average latency of potentials registered in girls from second group. Cognitive P300 amplitude waves are higher above central regions independently of the hand used.