In the study the levels decentration development obtained by Hughes and Piaget’s methods are compared both among themselves and with the levels of formation of classification, seriation logical operations and conservation principle understanding at preschool children. Statistically significant correlation interdependence (r-Spearman) between all investigated indicators is proved. The Piaget’s position on the importance of cognitive egocentrism as the starting point of child development, determined the logic thinking characteristics of the child was substantiated, it is necessary to consider all characteristics of logic thinking by designing and evaluating of decentration diagnostic methods. It is concluded that the Hughes and Piaget’s decentration diagnostic methods should be viewed as complementary rather than mutually exclusive when assessing the overall level of development of logical thinking of the child.