This paper deals with the role of peer interaction in cognitive development from the perspective of Piaget’s and socio-cultural approach. The description of original Piagetian and Vygotskian ideas regarding the mentioned phenomenon and their comparison is given in the first part of the paper. Research studies of Piaget‘s and Vygotsky‘s followers brought theoretical and methodological innovations in the examination of peer interaction influence on cognitive development. At the beginning they were devoted to different aspects of social interaction. Piaget‘s followers recognized the importance of peer interaction for cognitive development and created a rich corpus of empirical data. The authors from socio-cultural perspective, following Vygots...