Attention-Deficit/Hyperactivity Disorder (ADHD), due to its characteristic heterogeneity, is increasingly demanding the participation of multidisciplinary teams that take into account all the areas in which their knowledge and research are progressing. And, although we have been researching for 20 years in the area, even today, there are new elements that are emerging in the diagnosis and intervention of this disorder. Thus, we know that, in our country, 25% of children suffer some type of abuse or mistreatment in childhood, and that, as a consequence, some of these develop a post-traumatic disorder or a complex developmental disorder. Therefore, it is essential to advance in the discernment between ADHD and a disorder of this type, as, in addition in many cases, these events will not be explicit and/or verbalized by the minor. On the other hand, it is essential to resolve the relationship of ADHD with transdiagnostic elements, such as Slow Cognitive Tempo, to determine whether the two disorders will be overlapping or even comorbid and to understand the psychopathological and cognitive mechanism through which they are related. It is, therefore, necessary to advance in the knowledge of the differential diagnosis between the two. Another area that promises to contribute to the knowledge of evaluation and intervention in ADHD is psychophysiology, where electroencephalographic markers and endophenotypes represent a promising tool. Finally, we still need to fully characterize the amalgam of phenotypes that can occur, considering that the discovery of the distortion in the temporal estimation as a core symptom of ADHD is very recent, with all the derivatives that this will entail. However, we must know about this deficit and its characterization, to promote better clinical management in the evaluation and intervention of this disorder.