Introduction: Lower respiratory tract infection caused by respiratory syncytial virus is called bronchiolitis and is the leading cause of hospitalization in the winter months during the first year of life. Passive immunoprophylaxis of RSV infection is performed in high-risk infants of palivizumab according to specific indications. Palivizumab is the only immunoprophylactic agent currently approved for the prevention of bronchitis caused by RSV. Purpose: The primary aim of this thesis was to confirm the efficiency and safety of passive immunization with palivizumab in bronchiolitis prevention, caused by respiratory syncytial virus, according to the established indications, and to determine the tolerability of palivizumab and the side effects of any of the administered doses. Patients and results: Subjects were classified into two groups. One group of respondents were premature infants born with ≤ 32 gestational weeks, while the second group was subjects with inherited hemodynamically significant cardiac failure. The study was conducted retrospectively from November 2013 to April 2018 and included 105 patients receiving palivizumab at the Pediatric Clinic, Clinical Hospital Centre Rijeka. Results: The total number of respondents was 105. In the group of subjects under the age of ≥ 32th gestational week, there were 53. One girl from this group was affiliated with RSV bronchiolysis, hospitalized but did not develop complications. In the group of subjects with inherited hemodynamically significant cardiac failure there were 52 patients. One boy in this group had skin changes after the first dose of palivizumab. Of the other respiratory diseases, in the observed period, there were a total of 60 respondents, of whom 38 boys and 22 girls. Conclusion: This study has shown that palivizumab is an effective, safe preparation for the prevention of RSV bronchiolitis in children according to valid indications. The key is the prevention of RSV infection because it can easily and safely prevent most of the dangers of this disease in this sensitive patient population.