To analyze clinical characteristics and prevalence of rhinovirus infections in children in the hospital, we reviewed a retrospective dataset from a 20-year period, and conducted a short-term prospective study. Records of children and adolescents treated at our hospital during 1987-2006 with a documented rhinovirus infection were reviewed and compared with patients with other respiratory virus infections. Prospective study included all children >or=1 month of age admitted to pediatric infectious disease ward during an autumn period. Rhinoviruses were detected by reverse transcription-PCR and/or culture, and sequence analysis was used for virus typing. In the retrospective study, the median age of 580 children with rhinovirus infection was 1.9 years (interquartile range, 1.0-4.3 years), and 27% had an underlying medical condition. Eighty-four children (16% of in-patients) were treated at pediatric intensive care unit. Twenty-one children (4%) had a hospital-acquired rhinovirus infection. In the prospective study, rhinoviruses were detected in 28% of 163 hospital episodes. Acute wheezing illness was diagnosed in 61% of children with rhinovirus and in 31% of children with respiratory syncytial virus, enterovirus, or no study virus (P < 0.001). One-half of sequence-analyzed rhinovirus strains belonged to the newly identified C group. In conclusion, rhinovirus infections are a frequent cause of pediatric hospitalizations, and they are common also at the intensive care unit. Acute wheezing is the most frequent manifestation in hospital setting, but the range of clinical presentations is wide. Group C rhinoviruses may account for a large part of rhinovirus hospitalizations.