BACKGROUND: Acute exacerbations of respiratory diseases are a common cause of hospitalization among infants and children.AIM: To assess the epidemiological characteristics of asthma, bronchiolitis and croup among hospitalized children in Thessaloniki, from 1990 to 2003 included.METHODS: Data from the patient registry with discharge diagnosis "asthma", "bronchiolitis" and "croup" were analyzed retrospectively, in five Paediatric Departments of Thessaloniki. Age and sex of the patients, as well as the month of admission were taken into consideration.RESULTS: A total of 8762 admissions of children (aged 3 months-14 years) with the diagnosis of asthma, "bronchiolitis" and "croup", were identified. Sex distribution was 65.86% males (64.86% bronchiolitis, 65.26% asthma and 70.31% croup). Asthma admissions decreased by 53.65%, croup admissions decreased by 4.73%, while bronchiolitis admissions increased by 25.03%, during the study period. A clear seasonal variation was found in all the three diseases, with the lowest incidence during summer months. Moreover there were two peaks for asthma (one during spring and a second during autumn), one peak for bronchiolitis (during winter early spring) and one peak for croup (during autumn).CONCLUSIONS: Paediatric asthma and croup admissions have declined during the last 14 years, in contrast with bronchiolitis admissions, which showed an increased tendency. More frequent use of inhaled steroids and induction of asthma education programs may have contributed to decreasing asthma admission rates.