Introduction: Association between persistency of a patent ductus arteriosus (PDA) and morbidity in preterm newborns is still controversial. We aimed to investigate the relation between PDA and morbidity in a large retrospective study.Methods: A case-control study including neonates consecutively admitted to the Neonatal Intensive Care Unit (NICU), with gestational age (GA) ≤ 32 weeks or body birth weight (BW) ≤ 1500 g, over a 5-year period. Newborns were divided into Cases and Controls, according with the presence or absence of a hemodynamically significant PDA (hs-PDA).Results: We enrolled 85 Cases and 193 Controls. Subjects with hs-PDA had significantly (p<0.001) lower GA (26.7 w, 95%CI 27.1-28.0 vs. 30.1 w, 95%CI 29.7-30.4), BW (1024 g, 95% CI 952-1097 vs. 1310 g 95%CI 1263-1358) and an increased morbidity (60.0% vs. 18.7%). In a sub-group of extremely preterm newborns (GA < 29 weeks and BW < 1000 g), the rate of BPD was significantly increased in Cases (31.7%) compared with Controls (5.9%, p=0.033). Multivariate analysis showed that morbidity significantly depended on hs-PDA, GA and BW, and that, in extremely preterms, the hs-PDA represented an independent risk factor for BPD.Conclusions: The presence of hs-PDA seemed to increase the risk of morbidity in very low birth weight (VLBW) infants. In extremely preterm newborns, the risk of bronchopulmonary dysplasia (BPD) depended on the occurrence of hs-PDA.