Objective: The present study evaluated a 10-week psychosocial treatment designed specifically for children with attention-deficit/hyperactivity disorder (ADHD) and a comorbid anxiety disorder. Method: Using a nonconcurrent multiple baseline design, the authors treated 8 children ages 8-12 with ADHD, combined type, and at least 1 of 3 major anxiety disorders (separation anxiety disorder, generalized anxiety disorder, social phobia). The integrated treatment protocol involved parent management training for ADHD and family-based cognitive-behavioral therapy for anxiety. Pretreatment assessments included semistructured diagnostic interviews and other standardized measures to determine study eligibility. Children were randomized to 1 of 3 baseline control conditions (i.e., 2, 3, or 4 weeks) and subsequently treated in a university-based psychosocial treatment clinic. Weekly assessments of ADHD and anxiety disorder symptoms occurred throughout treatment and comprehensive assessments were obtained at pretreatment, 1-week posttreatment, and 6-months posttreatment. Results: Single-case results supported greater success in the treatment phase relative to the baseline phase for both ADHD and anxiety symptoms, and ADHD and anxiety symptoms appeared to change concurrently. Pre-post group analyses revealed significant and clinically meaningful improvements in ADHD and anxiety symptoms at 1-week posttreatment, but only anxiety symptoms moved into the subclinical range. At 6-months follow-up, treatment effects were maintained with new movement into the subclinical range for ADHD. Conclusions: The present study provides initial data on an integrated treatment protocol for ADHD and anxiety. Further replication and evaluation are needed. Implications of the findings are discussed. (Contains 2 tables, 1 figure, and 7 footnotes.)