The Strengths and Difficulties Questionnaire (SDQ) is a 25-item behavioural screening questionnaire developed by R. Goodman in the 1990s that assesses five scales: emotional symptoms, conduct problems, hyperactivity/inattention, peer relationship problems, and prosocial behaviour. The SDQ may be used in a pre-post effort to evaluate outcomes of implemented programs or interventions or as part of an initial screening or assessment of observed behaviours. For assessing low-risk or youth in a general population, an alternate three-scale division of internalizing problems, externalizing problems, and prosocial behavior may be used. The SDQ has an informant version that can be completed by teachers or parents and a self-report version for youth 11-17 years old. The SDQ in available in over 50 languages. Overseen by Youthinmind, Ltd., whose mission is to “promote the psychological well-being of people everywhere”, all versions of the SDQ and scoring instructions are available to download for free.