This group is pharmacologically stable. This group performs cognitive training through a therapeutic chess protocol designed by a chess psychologist. The training is done from home and we contact them weekly to correct the exercises done and to follow up.

These patients continue their stable pharmacological treatment and do not receive any additional cognitive intervention.

They are contacted weekly by phone to follow up on the group.

The SNAPIV is a scale for the assessment of ADHD symptoms. It consists of 18 scalar items from 0 to 3, of which 9 assess attention deficit and another 9 assess hyperactive-impulsive component. The cut-off points for attention deficit are 2.56 for teachers and 1.78 for parents. For hyperactivity-impulsivity they are 1.78 for teachers and 1.44 for parents. For both components, the points are 2 for teacher and 1.67 for parents.

The Conners scales are a set of scales for the assessment of patients with ADHD. This revised and abbreviated version of the Conners scale is designed to be answered by parents of children ages 6-18. It consists of 10 items with a Likert type response: 0= not true at all/never; 1= just a little true/occasionally; 2= Pretty much true/often; 3=very much true/very often.

The cut-off points are divided by gender. For children, a score above 16 is suspected ADHD. While for girls, a suspected diagnosis of ADHD is from 12 points

The BarOn is a questionnaire that it has 60-question, answered by children and young people from 7 to 18 years old. It provides information on total emotional intelligence, divided into four subscales: intrapersonal, interpersonal, stress management and adaptability. It also provides a general mood scale and other validation scales such as positive impression and inconsistency.

The ATENTO is a questionnaire in the process of validation that give a complete profile of the clinical symptoms of ADHD. This questionnaire has three parts: the first, with 125 items is common to all ages from 3 to 18 years. The second part, with 40 items had to be filled in if it was a patient from 3 to 6 years old and was not used in our study since the sample started from 7 years old. The third and last part, with 48 items, evaluated the population from 6 to 18 years old. All the items are of the likert type, and the parents can give scores of: 1= never or almost neves; 2= Rarely; 3= Sometimes; 4= Many times; 5= Always or almost always.

The Conners CPT-3 is a computerized, standardized, and validated application test for different age and gender groups. The test consists of pressing a button each time a letter (target) appears on the screen, except for the letter X (non-target), which should not be pressed. The duration is approximately 14 minutes and the presentation interval between letters is variable (1, 2 and 4 seconds). The test provides results on hits, error of omission (undetected target) and errors of commission (reacted non-target), which are considered a measure of impulsivity. In addition, CPT3-3 provides information on mean reaction time and reaction time variability of hits.

The UKU is a tool designed to evaluate possible secondary symptoms that happen during the week. This scale is not included in the assessment phases. Only the TSTM group should complete the scale after each cognitive training session.