The subject of the research was the analysis of the impact of bilingualism on cognitive development of the child. In the scientific literature there are two approaches to it, which are actual nowadays. One authors consider, that bilingualism harms cognitive development of the child. Other experimentally proves that bilingual children collide with two different styles of thinking, and various recognition of reality. Positive influence of the second language is observed when the language is acquired as consecutive bilingualism. The purposeful formation of bilingualism in preschool age not only covers the purpose – skill to communicate on each particular language, but also brings the contribution in cognitive development of the child.