Abstract. Background: None of the studies assessing effects of treatment of symptomatic duct on outcomes have considered heterogeneity of ductus arteriosus in terms of clinical and echocardiographic significance. Objectives: To characterize outcomes of neonates who received treatment for a haemodynamically significant ductus arteriosus and were classified according to the ductal staging system. Methods: Neonates were classified according to ductal disease severity score: clinical (C 1–4) and echocardiography (E 1–4) criteria (sum of C-score and E-score) as low-risk (composite score < 6), intermediate risk (composite score = 6) and high-risk (composite score > 6) groups. A comparative evaluation of neonatal demographics, respiratory outcomes and neonatal morbidities was made between low and high risk groups. Results: Data from 45 evaluations of the ductus arteriosus were analysed. Infants in high-risk group had significantly increased median transductal diameter [3.2 mm (2.7, 3.4) vs. 2.5 mm (2.4, 2.7), p = 0.02] and were more likely to require >1 course of indomethacin or surgical ligation. Infants with a high-risk stage were also more likely to require longer duration of oxygen support, home oxygen therapy and a higher, though statistically non-significant, trend for chronic lung disease. In the short term, at the end of the treatment course, no significant alteration in the ventilatory requirements was noted. Conclusions: Staging the ductus arteriosus may facilitate the identification of neonates at greatest risk of neonatal respiratory morbidity. It may also shed more light as to which babies, if any, benefit from therapeutic intervention. In this cohort, treatment with indomethacin did not reduce the morbidities assessed.