Knowing how long an infant with chronic lung disease (CLD) might require oxygen is a useful tool for counseling parents. We aimed to determine if carbon dioxide levels (PCO2) measured near term in newborn infants with CLD still requiring low flow oxygen would be useful in predicting their duration of oxygen requirement.A retrospective study was conducted on infants with CLD discharged from the neonatal unit on home oxygen treatment. The PCO2 levels of 64 infants measured by capillary gas after 34 weeks corrected gestation was correlated with duration of home oxygen requirement.We have shown that PCO2 levels measured near to term on a capillary gas sample in infants with chronic lung disease correlate with length of oxygen dependency (r = 0.55; p < 0.0001). However it was impossible to accurately predict the length of oxygen dependency in an individual case.We conclude that it would be unwise to predict an individual infant's duration of oxygen requirement using the PCO2 levels prior to discharge. However it might be possible to counsel parents in general that infants with lower PCO2 levels prior to discharge are likely to have their oxygen withdrawn more rapidly than those with higher PCO2.