This study introduces the Comprehensive Assessment of Defense Style (CADS), a new method to assess descriptively the defensive behavior of children and adolescents. Parents of 124 children and adolescents referred to a mental health clinic, of 104 nontreated children, and of 15 children whose fathers were treated for posttraumatic stress disorder completed the CADS Factor analysis of 28 defenses yielded one mature factor, one immature factor of defenses expressed in relations with the environment (other-oriented), and one of defenses expressed in relations with the self (self-oriented). The CADS significantly discriminated between patients and nonpatients. Psychiatric patients used more immature and fewer mature defenses than control subjects, and adolescents used more mature and fewer other-oriented defenses than children. Girls used more mature and fewer other-oriented defenses than boys. The reliability and validity data of the CADS are encouraging. The three defense factors may be implemented for diagnostic and clinical purposes as well as for screening for psychopathology risk in untreated populations.