The objective of this study was to investigate the percent of infections with adenovirus (ADV) in children who had pneumonia, acute bronchiolitis or viral respiratory infections and were admitted to two pediatrics hospitals in Bucharest (Grigore Alexandrescu Hospital and Alfred Rusescu Hospital). METHODS METHODS 70 children aged one month - five years, admitted to the above mentioned pediatrics hospitals in Bucharest, who were negative for the Respiratory Syncytial Virus (RSV) and the human Metapneumovirus (hMPV) by Reverse Transcription -Polymerase Chain Reaction (RT-PCR). 48 of them presented pneumonia upon admission to hospital, 6--acute bronchiolitis and 16 respiratory viral infections. Samples (nasal swabs) were taken from patients and introduced in viral transport medium. METHODS RT-PCR for RSV and hMPV, Multiplex PCR by seeplex multi-detection system with Seeplex RV/PB 18 ASE Detection for detection of 5 pneumonial bacteria and Real-Time PCR, Duplica Real Time Adenovirus Detection for ADV. RESULTS Of the total 70 patients negative for RSV, hMPV and 5 pneumonial bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila), 10 were ADV positive; none of the children < 6 months (N = 16) presented ADV infection. In the 6 months - 2 years group (N = 35), 6 were ADV positive. In the 2 - 5 years group (N = 19), 4 were ADV positive. CONCLUSIONS The percent of ADV infections in children hospitalized with acute respiratory infections (ARI) caused by neither RSV or hMPV is 14.2%. ADV is most frequently encountered in the 6 months - 2 years and then 2 - 5 years groups, but the most severe pneumonia forms can be seen in the 6 months - 2 years group. In children < 6 months with acute bronchiolitis ADV was not found to be an etiologic agent.