Lower respiratory infections are an important cause of morbidity and mortality in children, especially in newborns, infants and young children. We conducted a retrospective study and we analyzed the causes of death in newborns, infants and young children, in the necropsy protocols from two Departments of Pathology (Mureş County Hospital and Emergency County Hospital of Târgu Mureş, Romania), between 2016-2018. We performed descriptive statistics: number of necropsies per year, distribution by gender (male∕female), by place of origin (rural∕urban), by age and leading causes of death in our study. To establish the pattern of lung injuries, we performed a morphological, histopathological and immunohistochemical study [cluster of differentiation (CD) 3, CD14, CD20, CD31, CD34, CD68]. Our study is showing the most frequent and typical aspects of pulmonary pathologies in fetuses, newborns, infants and young children. In this way, we are highlighting the microscopic aspects of the immature lung, amniotic fluid and meconium aspiration, pulmonary distress syndrome in children, pneumonia, bronchopneumonia and vascular pulmonary disease developed in patients with congenital cardiac defects. Most deaths were recorded in the first 30 days or in the first year of life. Primary respiratory diseases were the leading causes of death in these patients. Secondary respiratory diseases were associated with the major causes of death in these patients as an aggravating or precipitating factor.