Background: in recent years, High Flow Nasal Cannula (HFNC) has been considered an alternative to non-invasive mechanical ventilation (NIMV) in severe asthma respiratory management in children. Objective: to describe the use of HFNC in children with severe asthma admitted to pediatric critical care unit (PICU). To compare its clinical characteristic and evolution with those receiving NIMV or other respiratory support. Methods: prospective observational study done in children admitted to PICU with severe asthma (October 2017 to October 2019). Data collected: epidemiological, clinical, respiratory support, thorax x-ray, pharmacological treatments and days of admission. Patients were divided into groups: 1) Only HFNC 2) HFNC and NIMV, and 3) Only NIMV. Results: Seventy-six patients included, 39 girls. The median age was two years and one month (range 160). The median pulmonary score was 5 (range 7). PICU admission lengths a median of 3 days (range 9), hospital 6 days (range 23). There were no epidemiological or clinical differences between groups. Children with only HNFC showed a shorter time of PICU days (p 0,025) and none of them required NIMV. In the group receiving both modalities, NIMV was used first and then HFNC in all cases. Children with HFNC showed higher SaO2/FiO2 ratio (p=0,025) and lower PCO2 level (p=0,032). There were no deaths. Conclusions: in our study the HFNC did not require escalation to NIMV and did not increase the length of PICU or hospital days. Normal initial blood gases and absence of high oxygen requirements were useful to select responders to HNFC.