Efficacies of the Incredible Years (IY) interventions are well-established in children with oppositional defiant disorder (ODD) but not among those with a primary diagnosis of attention-deficit/hyperactivity disorder (ADHD). We sought to evaluate 1-year follow-up outcomes among young children with ADHD who were treated with the IY interventions. Four- to 6-year-olds with ADHD ("n" = 49, 73% male) participated in 6 months of treatment using the IY parent and child interventions. Immediate posttreatment results indicated improvements in parenting, children's externalizing and attention problems, and social contact at school. At 1-year follow up, 22 of 27 variables that showed significant posttreatment effects demonstrated maintenance to 1-year follow up. Children with higher ODD symptoms at baseline showed more improvement in oppositionality and total behavior problems, and their mothers showed more improvement on harsh discipline scores. Approximately 70 to 75% of children were reported by their parents and teachers to fall below clinical cutoffs on measures of externalizing symptoms at the 1-year follow up (compared to 50% at baseline), and more than 50% fell below clinical cutoffs on measures of hyperactivity and inattentiveness (all were in the clinical range at baseline). Children with ADHD who were treated with the IY parent and child treatment programs showed maintenance of treatment effects 1 year after treatment. (Contains 5 tables.)