Updated project metadata. There is evidence that small extracellular vesicles (sEV) play a vital role in immune responses to viral and bacterial infection. Characteristics of urinary sEV, however, from pediatric patients with pneumonia remain to be ill-defined. In this study, we isolated sEV from urines of children with viral pneumonia or Mycoplasma pneumoniae pneumonia and healthy children and performed label-free proteomic analysis of these vesicles and identified viral-specific differentially expressed proteins compared with healthy children. Results of functional enrichment analysis suggest that the proteomic profiles of urinary sEV serve as the basis for understanding the fundamental biology of infection in children with viral pneumonia.