One hundred and twenty children with sinus node weakness were examined. The presence of functional pathology was diagnosed in most children using the cardiorespiratory synchronism test. It was also found that, in children with the sinus node weakness syndrome, their regulatory and adaptive capacities depended on their temperamental type and, hence, were predetermined genetically. This manifests itself in different degrees of weakening of the central link of the heart rhythmogenesis in the hierarchical system of the formation of the heart rhythm in the whole body, which determines the changes in the synchronization parameters when the cardiorespiratory synchronism test is performed in these patients.