Since the mid-90s, the number of children and teenagers diagnosed and treated for bipolar disorder has increased considerably. Yet, only a few of them actually had a diagnosis that was considered to be a "typical" bipolar illness. Indeed, the younger the child, the rarer is the bipolar disorder. Although the need to avoid a confusing terminology regarding bipolar disorder was generally accepted, agreement on diagnosis for this population was difficult to conclude particularly due to the net difference between North American and European clinical practices. In particular, the controversy concerned children and adolescents with chronic irritability and high comorbidity with attention deficit hyperactivity disorders (ADHD). In addition to having a clinical picture akin to mood disorders, these children frequently suffered from ADHD. The DSM-5 working group on mood disorders in children and adolescents proposed a new diagnosis: Dysruptive Mood Dysregulation Disorder (DMDD). This is a diagnosis still in evolution whose purpose is to avoid confusion between an emotional dysregulation and bipolar disorder. If the distinction with the latter appears clear, high comorbidity with ADHD is concerning and makes the nosological limits unclear.