Background: Rates of preterm birth have increased in most industrialised countries but data on later lung function of late preterm births are limited. A study was undertaken to compare lung function at 8?9 and 14?17?years in children born late preterm (33?34 and 35?36?weeks gestation) with children of similar age born at term (?37?weeks gestation). Children born at 25?32?weeks gestation were also compared with children born at term. Methods: All births from the Avon Longitudinal Study of Parents and Children (n=14?049) who had lung spirometry at 8?9?years of age (n=6705) and/or 14?17?years of age (n=4508) were divided into four gestation groups. Results: At 8?9?years of age, all spirometry measures were lower in the 33?34-week gestation group than in controls born at term but were similar to the spirometry decrements observed in the 25?32-week gestation group. The 35?36-week gestation group and term group had similar values. In the late preterm group, at 14?17?years of age forced expiratory volume in 1?s (FEV1) and forced vital capacity (FVC) were not significantly different from the term group but FEV1/FVC and forced expiratory flow at 25?75% FVC (FEF25?75%) remained significantly lower than term controls. Children requiring mechanical ventilation in infancy at 25?32 and 33?34?weeks gestation had in general lower airway function (FEV1 and FEF25?75) at both ages than those not ventilated in infancy. Conclusions: Children born at 33?34?weeks gestation have significantly lower lung function values at 8?9?years of age, similar to decrements observed in the 25?32-week group, although some improvements were noted by 14?17?years of age.