Introduction: Humidified high flow nasal cannula oxygen (HHFNCO) has increased in use in paediatric service with limited good quality studies. It might reduce PICU admissions in bronchiolitic patients, but there is no evidence that it reduces length of admission. Here the results of a service evaluation on the use of HHFNCO at Leeds Children’s Hospital during the bronchiolitic season 2016/17 are presented. Aims and Objectives: The aims were to assess patient characteristics of those going on HHFNCO, clinical area where it was commenced and outcome. Methods: Patients who were commenced on HHFNCO were identified through the handover sheets during the period of November 2016 to the end of February 2017. The data was assessed using MS Excel 2010. Results: During the study period 61 patients who started HHFNCO were identified. Out of 206 patients diagnosed with bronchiolitis during this time, 46 (22%) were commenced on HHFNCO. The average age of those starting HHFNCO was 3.5 months. Nine specific clinical areas were identified where HHFNCO was started, including PICU, HDU, Emergency Department, Respiratory ward, and Medical Admissions Unit. Being premature or having a congenital cardiac problem alone did not increase the risk of escalation of care. However, having more than one underlying comorbidity or having genetic disorder did. Not following the local guidelines was associated with escalation of care. Children with no pre-existing comorbidities who were started on HHFNCO did not require escalation of care. Conclusions: HHFNCO can be safely commenced in a variety of settings. Children with multiple pre-existing comorbidities commenced on HHFNCO were at higher risk of escalation of care.