Human bocavirus (HBoV) has recently been described as a common agent of acute upper and lower respiratory tract infections in children. We screened by polymerase chain reaction for HBoV nucleic acid nasopharyngeal aspirates from hospitalized children with negative culture and immunofluorescence assay for respiratory syncytial virus, influenza viruses, adenovirus, and parainfluenza viruses. HBoV was detected in 32 children (5.5%) and was the second virus identified in nasopharyngeal aspirates after respiratory syncytial virus. Most of the children had severe disease.