This retrospective observational study aims to evaluate clinical course of complicated community acquired pneumonia in children, particularly focusing on necrotizing pneumonia cases, as well as determination of etiological agents (viruses and bacteria) and its association to severity and outcomes of the disease. Furthermore, therapeutic approach, complications, short-term and long-term outcomes and the prevention of the disease are to be assessed. The study will encompass data from pediatric centers in the South-East Europe willing to participate in the study, encompassing ten-year period of time.