Background: Bronchopulmonary dysplasia (BPD) continues to be an important problem in neonates especially premature infants despite improved facilities of care, monitoring and treatment. Pulmonary hypertension (PH) is a major complicating factor and key cause of mortality in this population. Altered vascular and alveolar growth particularly in canalicular and early saccular stages of lung development following mechanical ventilation and oxygen therapy result in arrest of the lung development leading to BPD with PH. Early recognition of PH in infants with these risk factors is important for optimal management. We tested the hypothesis that asymmetric dimethylarginine, would be greater in infants with bronchopulmonary dysplasia associated pulmonary hypertension than in infants with BPD alone. The Aim: The aim of the current study was to measure the Asymmetric dimethylarginine (ADMA) levels, arginine levels & the plasma arginine-to-ADMA ratio in newborn infants with broncho-pulmonary dysplasia, to evaluate echocardiographic parameters among neonates with bronchopulmonary dysplasia, to correlate between plasma ADMA & arginine-to-ADMA ratio and echocardiographic (ECHO) parameters in those patients and to compare full term & preterm neonates with bronchopulmonary dysplasia as regard to plasma ADMA level. Methods: A case-control study was carried out of ninety (90) newborns selected from those admitted to Neonatal Intensive Care Unit at Maternity & Children Hospital and Alzhraa University hospital during the period from October 2015 to March 2018. Neonates were divided into 2 groups: Patient with BPD with PH (cases group): It included 45 neonates with BPD & PH, 35 preterm neonates and 10 full term neonates. Patient with BPD only (Control group): It included 45 neonates with BPD without PH. These 45 neonates were divided as 22 preterm neonates and 23 full term neonates.