Научный центр здоровья детей, Москва, Российская Федерация In a prospective study it was assessed the reliability of the questionnaire (calculating Cronbach's alpha coefficient), its validityby comparing the responses of patients who had a different ejection fraction (construct validity), and comparing the responses on the scales of PedsQL Cardiac Module questionnaire with the scales of the common PedsQL Generic Core Scale questionnaire (convergent validity). The questionnaire sensitivity was determined by calculating the difference between the values of quality of life of children at the moment of their first hospitalization (1st point) and in 4 months after the initiation of combination therapy (2nd point).Results: The study involved 61 children with heart failure (chronic myocarditis -25, dilated cardiomyopathy -36