We examined the degree to which child, family, and treatment variables predicted treatment outcomes for reading and math achievement and oppositional behavior in a sample of 135 young children (105 boys and 30 girls). All of the participants met "Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision" criteria for attention deficit hyperactivity disorder and received early intervention over a period of 24 months. Results of second-order latent growth model analyses indicated that (a) growth and posttreatment performance in reading and math were predicted by age, cognitive ability, gender, and lower perceived family support at pretreatment; (b) growth and posttreatment reading performance were predicted by child ethnicity; (c) posttreatment oppositional behavior was predicted by higher child hyperactivity-impulsivity symptoms at pretreatment, more hours of consultant contact, and receipt of psychotropic medication at pretreatment; and (d) parent attendance at education sessions was inversely related to improvement in oppositional behavior over time. Early intervention during the preschool years may yield significant improvement in reading and math skills for those children at greater risk of academic difficulties. Alternatively, children with milder symptoms and greater cognitive abilities may show the greatest improvement in oppositional behaviors.