In a sample of 55 preschool children, four to seven years of age, treated by a therapeutic day-treatment programme up to 3;4 years, developmental delays and behavioral disorders, rated by parents and preschool teachers, were assessed every five months until discharge. Developmental delays and behavioral disorders were reduced clinically and statistically significant between onset of treatment and discharge. This result could also be verified preponderantly by analysing several measurement points in parts of the sample with different treatment durations. Comparing changes during a waiting period of one year at most with changes during a waiting period of one year at most with changes during day-treatment of equal duration, treatment effects could be verified at least as a tendency for changes in behavior problems but not for developmental abilities due to methodological problems.