Biofeedback is increasingly used in practice due to diversity, the possibility of visualization of corrective functions, and the availability of objective indicators for assessing the dynamics of the training process. Biofeedback training helps to teach patients to skills that alleviate their condition, support active functioning, thereby increasing the quality of life. One of the simple methods of biofeedback is cardiorespiratory training, during which the patient learns the skill of diaphragmatic relaxation breathing, which is effective in rehabilitation for various pathologies, especially in pediatric practice. This type of biofeedback is based on the control of breathing and heart rate variability (HRV). HRV reflects the body’s ability to quickly recover from exposure to mental and physical stress factors. HRV is a unique marker of a person’s cardiovascular and psychophysiological health. This clinical example demonstrates a case of respiratory correction in a patient with comorbidities (multiple sclerosis, essential arterial hypertension, and panic disorder). The training was chosen as the most optimal for improving the patient’s quality of life, in respect that the leading complaint was panic attacks. One of the main goals of rehabilitation for this child is to teach the skills of diaphragmatic relaxation breathing, which allowed the patient learning to cope with future panic attacks, reduce anxiety and thereby improve his well-being. The article describes in detail the course of the training, recommended exercises for daily use, and presents the positive trend in the recorded indicators and the patient’s condition by the end of the course. Cardiorespiratory training is an effective and understandable method of rehabilitation that can be actively used in practice for an objective assessment of the classes performed and for psycho-emotional correction in children and adolescents with various pathologies.