Youth exhibiting symptoms of attention deficit hyperactivity disorder are frequently referred to school psychologists because of academic, social, and behavioral difficulties that they face. To address these difficulties, evidence-based assessment methods have been outlined for multiple purposes of assessment. The goals of this study were to delineate school psychologists' (a) primary purpose of their assessment of attention deficit hyperactivity disorder (i.e., screening, diagnosis, placement, intervention planning, progress monitoring), (b) use of recommended assessment tools/strategies and the perceived importance of each recommended tool/strategy for decision making, and (c) their perceived adequacy of training regarding attention deficit hyperactivity disorder assessment. Surveys from 217 school psychologists identified intervention planning as the primary purpose of assessment. Participants reported following recommended guidelines most frequently for diagnosis, impairment, and intervention development; they were least likely to follow guidelines for progress monitoring, evaluating outcomes, and assessing integrity. Participants reported being best trained for screening and placement, and least well trained in evaluating outcomes and developing interventions. Implications for practice and future research are discussed.