Attention Deficit/Hyperactivity Disorder (ADHD) is a complex neurodevelopmental syndrome defined symptomatically by levels of attention deficit/disorganization and hyperactivity/impulsiveness which are inappropriate for the person's age. The research program aims at better understanding the development, expression and treatment of ADHD. ADHD involves various phenotypic levels interacting throughout development (i.e., molecular, neurophysiological and neuropsychological, but also familial and social). Hence, my research program on ADHD is multidisciplinary. It is based on collaborations that allow recruiting and follow-up in an ADHD specialized clinic, as well as longitudinal follow-up of epidemiological cohorts (GRIP), using various methodological approaches (genetic, pharmacological, etc.) that are integrated with cognitive sciences and brain imaging. Attention deficit, disorganization, hyperactivity and impulsiveness are also found in other developmental disorders (e.g., associated with hypoxia/anoxia in children born prematurely or anticancer neurotoxic treatments, for example). The comparison of children with ADHD and other abnormal and normal developmental problems allow understanding the processes subtending these different attention syndromes, informing on potential causes of idiopathic ADHD.