The results of psychometric analysis of the new technique of thinking styles diagnostics are presented. The fundamental principles of thinking style concept by A. Belousova, according to which the thinking style is determined by the dominance of a person’s function in the structure of thinking activity during the problem solving, are covered. In accordance with A. Belousova’s ideas that the collaborative thinking activity as a self-organizing system is carried out by means of functions assumed by each participant: function of generating ideas, the function of selection (review and evaluation of information), functions of sense transfer and function of implementation. Thinking of adult, acting as a complex self-organizing system, combines the same functions: generation, selection, sense transfer and implementation. In this connection, we believe that the thinking style is defined as a characteristic set of functions actualized by a person in different situations of the problem solving. Domination of generation function determines the development of initiative thinking style, selection - critical, sense transfer - administrative, implementation - practical. The results of testing the reliability and validity of a new questionnaire for the thinking style diagnostics on a representative sample of Russians are given. The author’s version of the questionnaire is presented.