The chest x-ray (CXR) was the gold standard in the diagnosis of pneumonia in children. However, CXR has limitations and cannot discriminate in etiology. Current guidelines recommend against routine use of CXR in children with uncomplicated lower respiratory tract infections (LRTI). We used routine care data from a multicentre RCT including 597 children with LRTI symptoms, to evaluate the influence of CXR on antibiotic prescription in the emergency department (ED). CXR remains frequently performed in non-complex children suspected of LRTI in the ED (18%). Children who underwent CXR were more likely to receive antibiotics, even when adjusted for symptoms, hospital and CXR results. Our study highlights the inferior role of CXR in treatment decisions for children with LRTI as CXR, regardless of its results, is independently associated with more antibiotic prescriptions.