Introduction: Mental Disorders(MD) during adolescence are frequent in teenager age causing suffering and dysfunction on the psychosocial and educational development of adolescents. The aim of this survey was to detect the prevalence of MD among adolescents of 6^th to 9^th grade by application of Youth Self-Report for ages 11-18(YSR for Ages 11-18).

Methods: after parents and adolescents signed an Free Consent Term, the questionnaires YSR for Ages 11-18 were obtained from 2545 teenagers from 26 publics schools of Cascavel City-PR-Brazil. This survey had the approval of the Ethics Committee of Western Paraná State University under protocol CR number 955/2010

Results: 2545 pupils from 26 publics schools filled YSR, age ranged from11 to 14 years-old(mean:11,57 years), being female: 1609(63.2%) and male: 936(36.7%). About this total, 1039(40.8%) girls and 640(25.1%) boys were normal. MD syndroms observed on females were: Anxious/depressed: 231 cases, aggressive behavior: 104, social problems: 74, attention problems: 48, thought problems: 42, somatic complaints: 36, withdrawn: 25 and rule-breaking behavior: 10. On males: Anxious/depressed: 104 cases, somatic complaints: 59, social problems: 37, attention problems: 28, thought problems: 23, aggressive behavior: 17, withdrawn and rule-breaking behavior: 14 cases each.

Conclusion/Discussion: Rating scales of mental symptoms can be helpful in assessing adolescents patients, as YSR for Ages 11-18. This study showed that anxious/depressed was the most frequent as girls as boys, followed to aggressive behavior on females and somatic complaints in males. Prevalence de anxious/depressed(13,1%) was highest that the rate of depression in literature(6%).