Adenovirus is an important etiological agent of lower respiratory tract infections in all age groups. Its infections are very difficult to distinguish from other viruses and bacterial agents by clinical and laboratory findings. Although adenovirus is rarely causes acute respiratory distress syndrome, it has higher morbidity and mortality compared to other viruses. In this manuscript, an adenovirus infection in a pediatric patient with preliminary diagnosis of bacterial pneumonia by clinical and laboratory findings has been presented. Pneumonia has rapidly progressed to acute respiratory distress syndrome and the patient died despite extracorporeal life support treatments.