SUMMARY OBJECTIVE: Hemodynamically significant patent ductus arteriosus is a frequent problem in preterm neonates and may impair systemic and organ-specific oxygenation. Near-infrared spectroscopy provides a non-invasive tool to evaluate regional tissue oxygenation. The aim of this study was to investigate the effects of pharmacological closure therapy on cerebral, renal, and mesenteric tissue oxygenation in preterm neonates diagnosed with hemodynamically significant patent ductus arteriosus. METHODS: This prospective observational study was conducted in a tertiary neonatal intensive care unit between September 2021 and November 2024. Twenty-four preterm infants (24–34 weeks’ gestational age) with hemodynamically significant patent ductus arteriosus confirmed by transthoracic echocardiography were enrolled. Paracetamol treatment was given in cases where ibuprofen was contraindicated. Patients who underwent medical patent ductus arteriosus closure were divided into two groups: ibuprofen and paracetamol groups. Specific regional tissue oxygen saturation and fractional tissue oxygen extraction in three regions were monitored continuously using near-infrared spectroscopy for 72 h before and after medical treatment. Echocardiographic and hemodynamic parameters were recorded. RESULTS: While patent ductus arteriosus closure was achieved in 46% of cases with medical treatment, a significant reduction in patent ductus arteriosus diameter was achieved in 29% of cases. Ibuprofen was superior to paracetamol in reducing patent ductus arteriosus diameter. Mesenteric regional tissue oxygen saturation also improved significantly at 24–48 h in the ibuprofen group (p=0.01), while cerebral and renal oxygenation remained unchanged (p>0.05). CONCLUSION: Our findings revealed that ibuprofen therapy improved hemodynamic stability and mesenteric oxygenation in preterm neonates with hemodynamically significant patent ductus arteriosus. Although we showed in our study that there was no significant change in cerebral and renal oxygenation of hemodynamically significant patent ductus arteriosus with ibuprofen treatment, more comprehensive studies showing the changes with near-infrared spectroscopy are needed.