INTRODUCTION. Attention deficit hyperactivity disorder (ADHD) is one of the most frequent reasons for patients’ visits in everyday practice. The academic and social distortion it produces in those affected by this condition have turned it into a subject that is receiving growing attention from researchers and the progress being made in the neurosciences means that it is being investigated from a wide range of approaches. Genetic aspects, as well as anatomical and neurobiological markers, are some of the new lines of research that are being used together with a more precise neuropsychological approach to obtain a more comprehensive understanding of ADHD. Such knowledge now involves genetic factors, centres of cognitive disorder and the search for endophenotypes that account for the complexity of its semiology. DEVELOPMENT. The primary cognitive deficits in ADHD appear to be the underlying problem in the disorder, special attention also being given to both the executive functions and the distortion of the capacity to inhibit responses. Furthermore, anatomical factors have been related to the type and severity of the symptomatology of the disorder, although the dispersion of the results and the genetic findings that focus their attention on anomalous alleles for dopamine transporting and receptor genes suggest that the disorder is more complex. CONCLUSIONS. The different aetiological factors that have been associated to the disorder and the variability in the semiology of ADHD place us before a situation in disarray; the determination of endophenotypes, however, could enable us carry out a better systematisation of a disorder that is currently still a long way from being fully understood.