The new millennium was marked by the transition of humanity to a new stage of the development--the Information Society, which is an objective reality and affects on all aspects of living environment, including the health of children. The last decade was characterized by the increase of the use of means of informatization, the level of aggression and aggressiveness of children, the decrease of intellectual indices, deterioration of mental health, an increase of children with behavioral problems, hyperactivity, inattention, decrease of mental capacity. In a study on the example of preschool educational institution in the city of Irkutsk in the conditions of the changing of the informatization level of the society in the time period from 1998 to 2012, there were revealed the changes in indices of intellectual development, mental capacity and anxiety of children. Under observation there were 211 children aged from 5.5 to 6.5 years in the preschool institution of the central district of the city of Irkutsk. There were formed two groups of children: I group--children who attended kindergarten in 1998 and group II--children attending kindergarten in 2012. Age groups of preschool children were consistent with their calendar age: from 5 years 5 months 30 days to 6 years 5 months 30 days. In the study of intellectual development there has been shown the decrease of the number of children with average intelligence level and an increase in children with the below-average intelligence level, the increase of the speed (p < 0.05.) and the decrease of the quality (p < 0.05.) of the information processing in the Anfilov test for the mental performance and the increase the general level of anxiety, aggressive background and unmotivated fears "out" at the present time stage (2012).