Objective. To study asthenia in adolescents with attention deficit hyperactivity disorder (ADHD) and assess the efficacy of nooclerin. Material and methods. We examined 60 patients, aged from 12 to 15 years, with ADHD. A comparative analysis of ADHD demonstrated the predominance of an inattentive type (ADHD-I) and a combined type (ADHD-C). Results and conclusion. Symptoms of asthenia were found in 56% of adolescents with ADHD-C and in 96.7% with ADHD-I. The high efficacy and safety of nooclerin in the treatment of ADHD was demonstrated. The improvement of mental state was achieved in 76.7% of patients with ADHD-I and in 53.3% patients with ADHD-C.