Respiratory failure is one of the most common and critical problems in pediatric intensive care units (PICUs). The accurate precise assessment of respiratory failure and precise diagnoses of lung diseases are key issues in PICUs. Assessments by chest X rays (CXR) are common and prevalent for determining the reasons for respiratory failure in children. However, CXRs can be misread. Some patients may require chest Computed Tomography (CCT). CCT is essential for finding the abnormal region. However, in the PICU, the number of children who need CCT is small, and the risk of transporting unstable patients and the possibilities of malignancies are problematic. Lung ultrasound (LUS) has proven useful for detecting lung abnormalities in adults, but its usefulness is not clear in children.