Introduction: Absent ductus arteriosus (ADA) is a poorly described feature associated with tetralogy of Fallot (TOF). We compare characteristics and outcomes of neonates with symptomatic TOF (sTOF) with ADA to those with a ductus arteriosus (DA). Hypothesis: We hypothesized: neonates with sTOF and ADA would have similar outcomes to those born with a DA, and a small portion of the ADA cohort would have critically-deficient pulmonary blood flow (CDPBF). Methods: Consecutive neonates with sTOF who underwent intervention during the neonatal period from 2005—2017 were identified from the Congenital Cardiac Research Collaborative. Those with DA on echocardiogram performed on the first day of life or on fetal echocardiogram were identified and compared to those with ADA. ADA neonates who required ECMO or intervention to augment PBF on the first day of life were defined as having CDPBF. Patient characteristics and outcomes were compared between DA and ADA groups. Results: Among 519 neonates, 460 (89%) had a DA and 59 (11%) had ADA. ADA neonates were more likely to carry a genetic or syndromic diagnosis, had smaller branch PA sizes, and were more likely to receive a transannular patch compared to those with a DA. Despite this, reintervention rates were similar (data not shown), and there was only a small difference in mortality that did not reach statistical significance. Of ADA neonates, 7/59 (12%) had CDPBF. Compared to ADA neonates without CDPBF, those with CDPBF had lower baseline oxygen saturation (58 vs 87%, p=0.031) and smaller pulmonary valve (PV) annular z-score (-2.9 vs -2.5, p=0.015) with similar reintervention rates and mortality. Conclusion: ADA is relatively common in sTOF. Despite higher rates of comorbidities, mid-term reintervention rates and mortality are similar to those with DA. CDPBF is a rare, high-risk feature of infants with sTOF and ADA. Smaller PV size may be a marker of CDPBF. Future work should focus on prenatal factors to identify fetuses with TOF, ADA and CDPBF.