 Attention-DeficitHyperactive Disorder ADHD in adults is associated with global impairments and deficits in quality of life. The ADHD functional impairments during adulthood usually persist even after adequate medication treatment. The Skill Training Group of the Dialectical Behavioral Therapy DBT is one of the group therapies that had been adapted for the specific treatment of ADHD patients. Our primary aim is to explore the feasibility of the approach in different culture and to evaluate the efficacy of the Skill Training Group as an add-on treatment for adults using ADHD medication. This is a Randomized Clinical Trial comparing the Skill Training Group added to stimulants to treatment as usual only stimulants. 52 adults previously diagnosed with ADHD and treated with stimulants in our ADHD outpatient program will be enrolled. Only patients with residual symptoms will be included ADHD-Self Report Scale - ASRS 20. The intervention comprises the standard 12 sessions therapy program. The groups will have between 8 and 12 patients each, and will be conducted by a trained DBT therapist with supervision from a senior DBT therapist. The primary outcome will be the ASRS scores. Secondary outcomes include scores in ADHD Quality of Life, Becks Depression Inventory, Becks Anxiety Inventory, and performance in a neuropsychological test difference between pre and post-intervention Stop Signal Task. Adherence to the protocol will also be checked. The recruitment was initially scheduled for beginning in November. 