Bronchopulmonary dysplasia (BPD) is becoming a more prevalent problem as increasing numbers of extremely immature preterm neonates survive. This retrospective case control study was conducted in the (NICU) of Cairo University Hospital. The study included 100 premature neonates. All of them received O2 therapy, 50 infants developed BPD and 50 did not. There was a statistically highly significant difference between patients and controls regarding the duration of mechanical ventilation p <0.001, FIO2 P<0.001, TI &PIP (p<0.001, p=0.004 respectively).