Abnormal muscularization of intra acinar pulmonary arteries is a histological hallmark of persistent pulmonary hypertension of newborn (PPHN), an uncommon disease with high morbidity and mortality. PPHN presents with signs of respiratory distress immediately following birth. The disease is multi-factorial in origin and can be idiopathic as well associated with a variety of conditions such as congenital heart disease and both congenital and acquired lung diseases. We report two cases presenting as sudden unexpected death in late neonatal period (SUDI) showing abnormal muscularization of acinar pulmonary arteries reminiscent of PPHN. The significance of this report is twofold; to increase the awareness amongst pediatricians and pathologists of this feature not previously described in SUDI/Sudden Infant Death Syndrome (SIDS) and to highlight the importance of performing a thorough autopsy in order to identify the diagnosis.