Recognition of reasons for hospitalization of children can to great extent decrease the number of deaths through health and educational planning and preventive measures. The aim of the present descriptive study was to determine the causes of hospitalization among 0-12 Ys children referred to Qods pediatric hospital of Qazvin. Data were extracted from the medical records of 750 hospitalized children selected based on classified random sampling method during 2007. The most common groups of diseases were infectious and parasitic diseases (25.3%), respiratory diseases (20.8%), and prenatal disorders (15.2%) and the most frequent diseases were gastroenteritis (22.9%) and pneumonia (14.4%). According to our findings, conducting epidemiological studies and presenting health-educational program seem to be necessary to prevent and decrease the frequency of infectious and parasitic diseases, respiratory diseases, and prenatal disorders.