Background: Respiratory failure is the common cause leading to life-threatening in children with pneumonia. The classification of respiratory failure with hypoxemia and/or hypereapnia plays an important role in the management of respiratory failure. Aim: To determine the rate of hypereapnia and some factors relating to hypereapnia in children with respiratory failure due to pneumonia at the National Children's Hospital. Subject and method: A prospective, cross-sectional descriptive study of 157 patients with respiratory failure due to pneumonia (from 2 months to 5 years old) hospitalized at the National Children's Hospital between 01/01/2017 to 30/09/2017. Result: Hypereapnia was accounted for 38.9% of patients with respiratory failure due to pneumonia, This proportion of the under i-year-old group (43.7%) was higher than the 1-5-year-old group (19.4%). The higher percentage was found in the wheezing group (49.2%) as comparing to the nonwheezing group (32.7%). There is no statistical significant difference in the ratio of hypereapnia in the preterm and full term children, in the groups diat had reduction of breath sound and atelectasis, emphysema in X-ray, as comparing to the non these symptoms groups. Conclusion: Hypereapnia is common in children with respiratory failure due to pneumonia, especially in the under 1-year-old group. Besides oxygen therapy, removing CO2 is necessary.