Theoretical-methodical problems of psychodiagnostics are considered in the framework of system approach. The problem of connectedness and the necessity of informanional-structural synthesis are of first importance. System approach is used for the determination of measured individuality theory. The paradox of differences in theoretical and psychodiagnostical description of the same phenomenon may be overcome by way of "measured individuality" introduction. This theory takes the intermediate position between global theoretical models and specific research ones.