In Poland the majority of hospitalized cases of pneumonia (annually more than 70000) were reported without determination of an aetiological agent (J18 of ICD-10), also because diagnosis of viral ARTI is limited to identification of influenza viruses or sometimes RSV. MATERIAL AND METHODS: For determination the contribution of non-influenza viruses in ARTI among children, 381 nasopharyngeal swabs from hospitalized in period X.2008-IV.2011y. children (aged 1 day - 5 y.o.) were tested for RSV, HMPV, HEV/HRV, HPIV 1-3, HAdV, HBoV. RESULTS: At least one viral agent was detected in 72.7% of patients. The most predominant was RSV infection (49%), followed by HEV/HRV (15.5%); HMPV (8.7%), Adenoviruses (7.4%), HPIVt.1-3 (5.8%) and HBoV (5.5%). Seven periods based on the median of examined children/month were determined: 3 with increased number of ARTI. RSV infections, diagnosed in all periods, were predominate in five periods, mainly in LRTI cases. In the 3th period - HMPV was predominant, in the 5th - HEV/HRV. It was found that clinical manifestation of HMPV infections varied depending on the period. CONCLUSIONS: Relatively high prevalence of HBoV or HMPV cases of ARTI, especially different clinical picture in some periods (ARTI without pneumonia or bronchiolitis), indicated necessary of more detailed molecular and epidemiological studies. Also our results indicate the need for improved diagnostic capabilities of virological tests in acute upper and lower respiratory tract infections in children.