Early onset of behavioral disorders is predictive of long term adverse outcomes. There are some indicated and selective early prevention programs for attention deficit/hyperactivity disorder (ADHD), one of the most common behavioral disorders in childhood and adolescence. The purpose of this paper is to present a universal preschool program for preventing the development of ADHD related symptoms for children aged three to six. A total of 413 preschool children (experimental group (EG)1/4193; control group (CG)1/4220), and their teachers participated in the study. Children in the EG were randomized to two conditions: universal intervention (behavior modification (BM)1/499) vs additional ADHD specific elements (BM+attention training; BM+AT 1/494) to evaluate effects of a universal intervention vs additional ADHD specific elements. This is a quasi-experimental study, since due to time restriction half the preschools did not want to participate in the experimental study. Thus, participating children were not randomly assigned to the experimental and control conditions, though children were randomly assigned to two different treatments within the intervention group (EG1/EG2).