Approximately 15 to 25 percent of all adolescents experience psychosocial problems. The Strengths and Difficulties Questionnaire (SDQ) is widely used to screen for such problems. The studies in this dissertation provide insight into how useful the self-reported and parent-reported SDQ versions are among Dutch 12- to 17-year-olds in child and adolescent (mental) healthcare (Dutch: Jeugdgezondheidszorg, Jeugd Geestelijke Gezondheidszorg). The scales, especially of the parent-reported SDQ version, are useful for distinguishing between adolescents with psychosocial problems and those without such problems. Additionally, both SDQ versions, especially the parent-reported version, are useful for providing a preliminary indication of the type of psychosocial problems at hand (Anxiety/Mood disorder, Conduct/Oppositional Defiant Disorder, ADHD). The scales of the parent-reported version were also indicative of Autism Spectrum Disorders; the scales of the self-reported version were not. The use of the SDQ can be optimized by combining all scales of both SDQ versions into an SDQ profile. We found such profiles to be more useful for screening purposes than the so-called SDQ total difficulties scale was. In summary: The findings support the use of the SDQ among Dutch adolescents. Up until now, healthcare professional did not know if, and if so which, SDQ scales could be used for the benefit of adolescents. To inform them about the possibilities, and to help them interpret SDQ scale scores, a summary of the findings from this dissertation and new Dutch SDQ norms are presented in a manual that has been distributed among users of the SDQ (https://assets.ncj.nl/docs/a299fba5-d5e3-4c96-8d90-0605c185b0d9.pdf).