{Reference Type}: Journal Article {Title}: Diversity and representation in ADHD psychosocial treatment research: A comprehensive synthesis with data from over 10,000 participants. {Author}: Merrill BM;Hare MM;Piscitello J;Schatz NK;Fabiano GA;Wells EL;Robertson EL;Aloe AM;Pelham WE;Macphee F;Ramos M;Zhao X;Altszuler AR;Javadi N;Morris SSJ;Smyth A;Ward L;Jones HA; {Journal}: Clin Psychol Rev {Volume}: 112 {Issue}: 0 {Year}: 2024 Jun 13 {Factor}: 11.397 {DOI}: 10.1016/j.cpr.2024.102461 {Abstract}: Demographic data from nearly 50 years of treatment research for children and adolescents with attention-deficit/hyperactivity disorder (ADHD) are synthesized. Comprehensive search identified ADHD treatment studies that were between-group designs, included a psychosocial, evidence-based treatment, and were conducted in the United States. One hundred and twenty-six studies that included 10,604 youth were examined. Reporting of demographics varied with 48% of studies (k = 61) reporting ethnicity, 73% (k = 92) reporting race, 80% (k = 101) reporting age (M age = 8.81, SD = 2.82), and 88% (k = 111) reporting gender. Most participants identified as non-Hispanic/Latine (15.99% Hispanic/Latine), White (62.54%), and boys (74.39%; 24.47% girls). Since the 1970s, zero youth in ADHD treatment studies identified as Middle Eastern/North African, 0.1% were American Indian/Alaskan Native or Native Hawaiian Pacific Islander, 1.77% were Asian, 15.10% were Black, and 3.14% were Multiracial. Based on publication year, the proportions of girls, racially minoritized youth, and Hispanic/Latine youth included in ADHD treatment research have increased over time. Girls, non-binary and non-cisgender youth, young children, adolescents, Hispanic/Latine youth, and youth from all racial groups other than White are underrepresented in ADHD treatment research. Research gaps are discussed, and recommendations for comprehensive demographic reporting in child and adolescent psychological research are provided.