Intellectually gifted students with attention-deficit/hyperactivity disorder (ADHD) face unique academic and social challenges, yet little research has been conducted with this population. The purpose of this study was to examine the self-esteem and self-concept of intellectually gifted children with and without a coexisting diagnosis of ADHD. Data were gathered from 112 children, aged 6 to 18, identified as having high cognitive ability (IQ of 120, 91st percentile, or above); 54 participants also met diagnostic criteria for ADHD. Despite having similar IQs, gifted students with ADHD had lower scores on measures of self-esteem, behavioral self-concept, and overall happiness than gifted students without a comorbid diagnosis. Among all participants, children had higher reported overall happiness than adolescents. Professionals working with gifted students with ADHD should be aware of the potential for coexisting self-esteem difficulties and, if warranted, address these issues in educational and clinical environments. (Contains 6 tables.)