Background. Even though until recently it was believed that ADHD is a primarily childhood condition, once the adult diagnostic criteria was introduced in DSM 5, the clinical interest for this disorder increased, and it's nowadays recognized that adults continue to experience high levels of clinically significant symptoms. Methods. In this observational, retrospective study we investigated the evolution of psychiatric diagnosis to adulthood in a group of patients that received an ADHD diagnosis before turning 18. In the study it's been used the information data base of „Prof. Dr. Alex. Obregia” Psychiatry Hospital. In the period January 2009-December 2018 in Child and Adolescent Psychiatry Department there were assessed 2.628 children/ adolescents that met the criteria for an ADHD diagnosis. 58 patients returned to the same hospital after turning 18 years of age. Results. ADHD diagnosis was maintained in 5 out of the 58 patients. 61.40% of the adult patients had a Personality Disorder. 25% of the patients had behavioral disorders secondary to drug use, and 73.33% of subjects with chronic substance abuse had comorbid a personality disorder. Regarding the Affective Disorders, 65% of the patients presented episodes of unipolar Depression, while 35% had Affective Bipolar Disorder. Conclusions. The obtained data are consistent with those in the literature. The highlighted results demonstrate that there is a need for increased awareness in terms of continuity of ADHD diagnosis in adulthood, because this disorder is still underdiagnosed and less treated in adult life.