Background Acute respiratory infection (ARI) is one of the most common infectious diseases in infants and young children globally.This study aimed to determine the virus profile in children with ARI presenting with different severities.Methods Clinical specimens collected from children with ARI in Beijing from September 2010 to March 2011 were investigated for 18 respiratory viruses using an xTAG Respiratory Viral Panel Fast (RVP Fast) assay.The Pearson chisquare analysis was used to identify statistical significance.Results Of 270 cases from three groups of ARI patients,including Out-patients,In-patients and patients in the intensive care unit (ICU),viruses were detected in 176 (65.2％) specimens with the RVP Fast assay.The viral detection rate from the Out-patients group (50.0％) was significantly lower than that from the In-patients (71.1％) and ICU-patients (74.4％) groups.The virus distribution was different between the Out-patients group and the other hospitalized groups,while the virus detection rate and distribution characteristics were similar between the In-patients and ICU-patients groups.The coinfection rates of the Out-patients group,the In-patients group,and the ICU-patients group were 15.6％,50.0％ and 35.8％,respectively.In addition to respiratory syncytial virus (RSV) and adenovirus (ADV),human rhinovirus (HRV) was frequently detected from children with serious illnesses,followed by human metapneumovirus (hMPV),human bocavirus (HBoV) and coronaviruses.Parainfluenza virus 3 (PIV3) was detected in children with lower respiratory illness,but rarely from those with serious illnesses in the ICU-patient group.Conclusion In addition to so-called common respiratory viruses,virus detection in children with ARI should include those thoucht to be uncommon respiratory viruses,especially when there are severe ARI-related clinical illnesses.