The effectiveness of neurofeedback has been evaluated in a 30-session theta/beta frequency band training with six children of the same age with comparable verbal and nonverbal intelligence. Five of them have not disclosed any neuropsychological or other neurological abnormalities and formed the control group, while the subject AS had an attention deficit/hyperactivity disorder. Before, and seven months after training, the attention levels of both groups were measured by the d2-R Attention Stress Test. The evaluation of this test showed that AS improved significantly across all scales of attention performance (concentration power, processing speed and number of errors). At the same time, the theta/beta ratio was reduced during the neurofeedback training in AS from the 17th and in the control group from the 14th session.