Objectives: To determine whether passive smoking increases the frequency of respiratory infections in children; does the number of cigarettes smoked per day inside the home correlates with frequency of respiratory infections in children; is there a connection between the frequency of respiratory infections in children and smoking of a particular parent; whether passive smoking increases the frequency of respiratory infections in children with allergic diseases; is there a difference in frequency of respiratory infections between male and female children exposed to passive smoking. Design: A retrospective cohort study was conducted. Settings: The study was conducted in the pediatric clinic of primary health care Dr. Mira Pavlov, Sućidar 79, in Split. Patients and methods: The study included 203 children, aged between 1 and 7,5 years, who were brought to a pediatric clinic by parents for a medical examination. Children were divided into two groups: a group of 114 children whose household members smoke, and a group of 89 children whose household members don't smoke. We analyzed the frequency of respiratory infections in the last two years. All the necessary data has been obtained by a questionnaire filled out by parents and by inquiry into the medical documentation on the computer. Results: The difference in the frequency of bronchitis between the group of children whose household members smoke and whose household members don't smoke is on the border of statistical significance (P = 0,052). The number of bronchitis is statistically significantly higher in the group of children whose household members smoke inside the home compared to the group of children whose household members don't smoke (P = 0,008). The number of cigarettes smoked per day inside the home statistically significantly correlates with the number of bronchitis in children (P = 0,003). Maternal smoking statistically significantly increases the number of pneumonias in children compared to paternal smoking (P = 0,001). Children with allergic diseases whose household members smoke don't have statistically significantly higher number of respiratory infections compared to children with allergic diseases whose household members don't smoke. There is no statistically significant difference in the frequency of respiratory infections between male and female children whose household members smoke. There is no statistically significant difference in social status and education between families whose household members smoke and families whose household members don't smoke, except in father's qualifications. Conclusion: Passive smoking increases the frequency of bronchitis in children aged between 1 and 7,5 years. Number of cigarettes smoked per day positively correlates with a number of bronchitis in children. Maternal smoking increases the number of pneumonias in children compared to paternal smoking. Children with allergic diseases whose household members smoke don't have a higher number of respiratory infections compared to children with allergic diseases whose household members don't smoke. There is no difference in the frequency of respiratory infections between male and female children whose household members smoke.