This systematic review and meta-analysis aimed to determine the accuracies of a broad range of screening tools for attention-deficit/hyperactivity disorder (ADHD) in children and adolescents, and to compare the diagnostic accuracy of tools between population-based and clinical/high-risk samples, and across reporters.MEDLINE, PsycINFO, EMBASE, and PubMed were searched up until February 20, 2020, with no language restrictions. Studies reporting diagnostic accuracy of a screening tool against a diagnosis of ADHD in children and adolescents <18 years of age were eligible for inclusion. Meta-analyses were undertaken to provide pooled estimates of the area under the curve (AUC), and sensitivity and specificity of groups of measures.A total of 75 studies published between 1985 and 2021 reporting on 41 screening tools that were grouped into 4 categories (Achenbach System of Empirically Based Assessment [ASEBA], DSM-IV symptom scales, SDQ, and Other Scales) were retained. The pooled AUC for studies using a combined ADHD symptoms score was 0.82 (95% CI = 0.78-0.86), although this varied considerably across reporters (0.67-0.92) and populations (CI = 0.60-0.95). None of the measures met minimal standards for acceptable sensitivity (0.8) and specificity (0.8).Most tools have excellent overall diagnostic accuracy as indicated by the AUC. However, a single measure completed by a single reporter is unlikely to have sufficient sensitivity and specificity for clinical use or population screening.