The article presents modern views on the problem of bronchial asthma and allergic rhinitis as a comorbidity in children. The concept of single chronic allergic respiratory syndrome is considered. Following international and national recommendations for the management of patients with bronchial asthma and allergic rhinitis, the impact of leukotriene receptor antagonists in the treatment of this comorbidity is determined. The compliance in the treatment of children with bronchial asthma and ways of its optimization are given. The use of montelukast sodium in the treatment of the persistent forms of allergic rhinitis and bronchial asthma in children is scientifically substantiated. The treatment outcomes for the control therapy of mild persistent forms of bronchial asthma and allergic rhinitis in children aged 2–6 years with such leukotriene receptor antagonists as montelukast sodium are shown.