Introduction: Bronchiolitis is an acute viral infection of the lower respiratory tract that primarily affects infants and children under two. Aim: To compare treatment outcomes before and after the implementation of non-invasive ventilation and determine whether non-invasive ventilation has influenced treatment outcomes such as shorter oxygen dependency and hospitalisation duration. Materials and Methods: A retrospective analysis of medical records was conducted on 202 children hospitalised for bronchiolitis at the Department of Pediatrics, Clinical Hospital Center Rijeka, over six years (January 1, 2017, to December 31, 2022). Results: The average age of hospitalised children was six months (range: 10 days to 4 years). The majority were male (64%). Thirty-three (16%) were born prematurely (gestational age: 24-36 weeks). The average duration of hospitalisation was 5.1 days (range: 1-27 days). The respiratory syncytial virus (RSV) presence was confirmed in just over half of the children (55%). Approximately the same proportion received oxygen therapy (54%), either through a mask or nasal cannula (65%), high-flow oxygen therapy (HFOT) (40%), or non-invasive ventilation (NIV) (11%). The duration of hospitalisation was shorter during the COVID-19 pandemic for children receiving HFOT or NIV compared to the pre-pandemic period. A significant difference was also observed in the number of children treated with HFOT, which nearly doubled during the pandemic. Cases of RSV bronchiolitis in August were recorded during the COVID-19 pandemic, which was not seen in the previous period. Conclusion: Treatment with HFOT is becoming increasingly common in children with moderate to severe bronchiolitis. If applied, it affects the reduction of hospitalization duration and faster recovery.