Background: Pneumonia is a leading cause of mortality in children. Despite more than 50% of pneumonias are due to viruses, because it is difficult to rule out bacterial etiology, initial management of pneumonia in children usually includes antibiotics, often unnecessary. In 2006 was designed and validated a clinical prediction rule (BPS: Bacterial Pneumonia Score) which accurately identifies hospitalized children's risk of bacterial pneumonia. However, BPS efficacy on guiding therapeutic decision in children with community acquired pneumonia (CAP) has not been yet assessed.