Hyperactivity is now called ADHD for Attention Deficit Disorder with or without Hyperactivity. ADHD with hyperactivity is often confused with bipolar disorder. It is a behavioural disorder that can cause problematic behaviour with serious repercussions on social life. Early diagnosis and management are thus very important. The causes are probably multiple and remain a subject of study and debate. Listed among the possible causes are: brain lesions, due for example to lack of oxygen at birth; a genetic origin of dysfunctional brain areas involved in the control of attention and movement (dysfunctions which may also be found in the patient’s parents); a poor intra-uterine environment due to alcohol consumption and smoking during pregnancy or even pesticides present in food. Symptoms are usually different in childhood (where we see restlessness, inability to remain still, with constant hand and foot movements and extreme verbosity...) and in adulthood with reduced physical restlessness and sports involvement with poor behavioural control, varying substantially between from one person to another.