Objectives: To evaluate feasibility and preliminary effects of a new group treatment manual for adults with ADHD and to explore adherence to treatment and its relation to outcome. Method:Eighteen adults with ADHD recruited from neuropsychiatric units in Stockholm underwent a 14-week program including combined cognitive and dialectical behavior therapy. Assessments were made at baseline, posttreatment, and follow-up, at one and six months after treatment end. Primary outcome measure was the Adult ADHD Self Report Scale version 1.1. Results/Conclusion: ADHD symptoms significantly decreased (d = 1.29) and remained stable for 6 months. Measures of depression, perceived stress, and anxiety were also significantly reduced. Attendance and patient satisfaction was high. Use, comprehension, and perceived benefit of treatment components varied from medium to high. Total use of treatment components was, in general, positively correlated with favorable outcome. The current combination of treatment components may be a valuable addition to available treatments in psychiatric care.