Aims: To determine if HFNC use was associated with changes in incidence of BPD and ROP. Methods: This retrospective study examined premature infants (<30 weeks GA or <1500g) in a tertiary neonatal unit from 2010-2016. Patients were compared before and after introduction of HFNC. Further analysis of high-risk infants (<28 weeks GA or <750g or ventilated) compared those who received HFNC to those who did not across the whole period. Primary outcomes were incidence of BPD and ROP requiring surgery. Results: Incidence of BPD rose following the introduction of HFNC (82/232 (35.3%) after vs 33/251 (13.1%) before, p<0.001). On multivariate analysis, the chance of developing BPD after HFNC introduction remained higher (OR 4.353, 95% CI2.546-7.443). More infants received surgery for ROP following HFNC introduction (0/214 vs 11/205 (5.4%), p=<0.001). In the second analysis, the rate of BPD was higher in those who received HFNC (90/132 (68.1%) vs 33/153 (21.6%), p<0.001). Receiving HFNC demonstrated higher chance of BPD in multivariate analysis (OR 7.802, 95% CI 4.223-14.423). Rate of ROP surgery was higher in those who received HFNC (0/153 vs 13/134 (9.7%), p<0.001). Conclusions: In this study, use of HFNC was associated with significantly increased risk of adverse outcomes.