Little is known about the development of maximal flow at functional residual capacity, a measure of airway patency, in infants with chronic lung disease (CLD). In a follow-up study, we evaluated V'maxFRC in very low birth weight infants with CLD, treated with high-frequency oscillation ventilation (HFOV) or conventional mechanical ventilation. In 36 infants with CLD, V'maxFRC was evaluated at 6 and/or 12 months corrected age, and the relationship between perinatal factors and lung function was studied. Mean (SD) birth weight and gestational age were 837 (152) g and 26.8 (1.7) weeks, respectively. At 6 and 12 months, mean V'maxFRC was significantly below normal. Between 6 and 12 months, there was a mean (95% confidence interval) reduction in V'maxFRC (Z score) of 0.5 (0.2-0.7) (p < 0.001). At 12 months, the mean V'maxFRC (Z score) was higher for children initially treated with HFOV (n = 15), as compared with children treated with conventional mechanical ventilation (n = 16): mean (95% confidence interval) difference was 0.6 (0.2-1.0) (p = 0.008). We conclude that very low birth weight infants with CLD have decreased V'maxFRC that worsen during the first year of life. Initial treatment with HFOV was associated with a more favorable outcome of V'maxFRC at 12 months corrected age.