The article presents an overview of classic and modern research concerning the role of neuromarkers in the diagnosis of attention-deficit/hyperactivity disorder (ADHD) and biological correlates of this disorder associated with the dysfunction specific brain structures. ADHD is the most difficult area to diagnosing neurodevelopmental disorders due to the lack of permanent diagnostic criteria of this disorder and comorbidities, and also a large diversity of symptoms. Some of the criteria for this disorder such as age also have little diagnostic value and require a new discussion. In the circumstances of difficulties in diagnosis may help study of neuromarkers of ADHD, derived by analyzing the patterns of brain electrical activity in the EEG. Thus diagnosis may become easier, faster, and most importantly, more accurate.