Pervasive developmental disorders represent obviously a heterogeneous group of disorders, whose clinical expressions, courses and prospects differ significantly. Common to all these disorders, expect essential diagnostic characteristics, is the fact that they are life-long problems, thus, these are disorders without possibility of complete relief. Although measures of secondary prevention in these disorders do exert a limited effect, it is possible to achieve indubitable improvements in three fields:· well-timed application of adequate treatment may influence the essential characteristics of a disorder in the direction of adaptation to requirements of social environment, improvement of communication and enrichment of poor activity repertoire;· slowing down and delaying of unfavorable disorder evolution and· helping in understanding, accepting and adapting of child’s family to a pervasive developmental disorder.Value of early established diagnosis is not reflected only in foundation of organized adequate treatment. Early established diagnosis enables a well-timed giving of genetic advice to the family which is, as a rule, young, and without genetic load. On the other hand, well-timed diagnosis enables planning of life-long complete care for the patient with the disorder.