Inclusion Criteria:  Gestational age - <32 weeks OR birth weight < 1500 grams Postnatal age ≤ 28 days Meets criteria for hsPDA Clinician's decision to treat PDA  Exclusion Criteria:  Contraindication for administration of Ibuprofen (cyclooxygenase-inhibitors) or Paracetamol, such as: active bleeding (e.g. intracranial or gastrointestinal haemorrhage), thrombocytopenia (<50x109/L), renal failure (raised creatinine (>100 micromole/l) or oliguria (<0.5 mL/kg/hour), known or suspected necrotising enterocolitis, any gastric or intestinal perforation, pre-treatment abnormal liver function tests (ALT > upper normal limit of the reference range, Bilirubin > National Institute of Clinical Excellence exchange phototherapy level). Previous use of Ibuprofen or Paracetamol prior to randomisation. Persistent pulmonary hypertension (ductal right-to-left shunt ≧33% of cardiac cycle). Congenital heart defect, other than PDA or Patent Foramen Ovale (PFO). Life-threatening congenital birth defects. Chromosomal abnormalities and/or congenital anomalies associated with abnormal neurodevelopment.