The aim of this study was to determine the influence of gestational age at birth, postnatal age, specific complications and methods of treatment on the lung hyaluronan concentration in infants. Lung samples and clinical records from 117 infants who died 0–228 days (32 weeks) after preterm or term birth were studied. The lung hyaluronan concentration at death was most strongly associated with the gestational age at birth, an association best described by an exponential function with a negative power coefficient. After adjustments for gestational age, the lung hyaluronan concentration also correlated significantly with birth weight, weight at death, the wet-to-dry lung weight ratio and specific staining for hyaluronan in the pleura. Intrauterine infection was also associated with a significantly higher lung hyaluronan concentration.