Aggressive/attacking and helpful/emphatic/prosocial behaviors are extremely important in human relationships. Both high levels of aggression and deficits of prosociality play important role in the development and conservation of mental disorders. We review the measurement options and clinical importance of aggressive and prosocial behavior. The typical developmental pathways and the genetic and environmental background of these behaviors are presented. The clinical tools used in the measurement of aggression and prosociality are summarized in the present paper, with specific attention on questionnaires applied in Hungarian practice. The connections between diagnostic categories (conduct disorder, oppositional-defiant disorder, attention deficit and hyperactive disorder, autism spectrum disorders) and the two behaviors are evaluated. In the end, we present those additional research projects that explore the cognitive-emotional background of aggressive or prosocial behavior with clinical relevance either in the diagnosis or in the treatment of child psychiatric diseases.