The own research results concerning lies of children between 7 and 9 years of age are presented in the article. The study group of children was consisted of 137 pupils of early school education, including 68 girls and 69 boys. The factual material collected during individual conversations with children allowed answering the research questions: how do children in primary school age define the lie, and what are similarities and differences in verbal definitions of the lie given by girls and boys.