Flexibility of thinking in pre-school children has been largely neglected by researchers. In the author's definition thinking is a process of using (by a child) of specific thinking means. An original experimental procedure used in the study reveals that the flexibility of thinking, understood as an ability to reconstruct available means of acting, depends on the ability on the part of a child, first, to find in the mental tools which he/she already posesses some new qualities and aspects, and second, to use the previously used thinking tools in new contexts.