The study was aimed to define the indicators of cognitive and psychomotor development of 4-year-old children to identify the potential risk zone of possible developmental delay (DD). The study sample consisted of 628 4-year-old children from different educational institutions of St. Petersburg, including 575 typically developing children and 53 children with DD. For data collection the tool "Multifactor study of mental development" was used in form of test tasks (dichotomous 123 tasks), as a part of software complex for longitudinal researches, in the following areas: motor skills, cognitive abilities, social intelligence. A structural mathematical model was developed based on the results of the study allowing assessment of the probability of a child belonging to a Norm group or to a DD group. It was determined that four factors (scales) make the greatest contribution to the differential diagnosis of typical development from DD (in descending order of importance): psychomotor coordination, verbal and conceptual thinking, general awareness and short-term memory. The high accuracy of prognosis of child's development was shown by means of the presented method regardless of age: for all sample of 4-year-olds, and for younger and their senior subgroups (not less than 95%). It was discovered that the main predictor of the child's belonging to the Norm group or to the DD group was the G-factor (general abilities), the indicators of which are the selected four scales. The assumption was confirmed about the indirect influence of age on the prediction of the diagnosis: age directly affected the selected abilities, which, in turn, were indicators of the General ability factor. At the same time, the influence of age was revealed only in relation to a group of typically developing children, and to a greater extent — in relation to its younger subgroup. The test norms of development were elaborated for the general (total) scale of development and for the four selected scales, adequate throughout the age range of 4-year-olds, the validity and reliability of these scales were substantiated.