Objective <p>To evaluate the accuracy and reliability of capnometry in neonates undergoing inter-hospital transport.</p> Study design <p>A prospective observational cohort study of ventilated neonates transported by the National Neonatal Transport Programme (Ireland). End-tidal CO₂ (etCO₂) was compared with blood gas pCO₂ at the start and end of transport using intraclass correlation coefficients (ICC) and Bland–Altman analysis. Secondary outcomes included capnometry trends and the effects of lung disease and transport duration on capnometry values.</p> Results <p>A total of 150 neonates were enrolled. ICC values were 0.61 (95% CI 0.50–0.70) pre-transport and 0.52 (95% CI 0.40–0.63) post-transport, indicating moderate agreement. On average, capnometry underestimated blood pCO₂ by ~1 kPa (7.5 mmHg). Approximately 70% of patients showed concordant directional changes, though the magnitude varied between individuals.</p> Conclusion <p>Capnometry may provide a useful non-invasive tool for monitoring CO₂ trends during neonatal transport, despite underestimating blood pCO₂ by ~1 kPa (7.5 mmHg).</p> Keynotes <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Capnometry is a non-invasive method that measures end-tidal partial pressure of carbon dioxide in the expired gas.</p> </ItemContent> <ItemContent> <p>There has been limited data on the use of capnometry in neonates, particularly during neonatal transport, and the published studies report conflicting results.</p> </ItemContent> <ItemContent> <p>This study suggests that capnometry may be a useful tool to monitor CO2 and trends during neonatal transport.</p> </ItemContent> </UnorderedList></p>