In a prospective study of developmental outcomes in relation to early-life otitis media, behavioral, cognitive, and language measures were administered to a large, diverse sample of children at 2, 3, 4, 6, and 9–11 years of age (N = 741). At 9–11 years of age, 9% of the children were categorized as having attention-deficit/hyperactivity disorder (ADHD) based on parent report. Compared to the non-ADHD group, the ADHD group had higher (i.e., less favorable) scores on parent and teacher versions of the Child Behavior Checklist at all ages. Children in the ADHD group also had lower scores on cognitive and receptive language measures in preschool. The findings support the concept that ADHD is a cognitive as well as a behavioral disorder.