Background: Lung function is traceable from infancy to adulthood. Only a few studies have examined lung function from birth to childhood longitudinally in children born moderate to late preterm. We aimed to investigate how prematurity and lung function in the neonatal period are related to lung function and respiratory morbidity at age 6 in former moderate to late preterm children compared with children born at term. Methods: Lung function was measured in a cohort of moderately to late preterm (n = 48) and term-born (n = 53) infants in the neonatal period by FeNO, and tidal breathing flow-volume loops (TBFVL) and at age 6 (n = 52) by spirometry, whole-body plethysmograph and impulse oscillation combined with a respiratory symptom questionnaire. Results: Moderate to late preterm children had a higher T_PEF/T_E ratio neonatally (42.6% vs. 33.7%, p = 0.02) and a lower % predicted orced expiratory volume in the first second at age 6 (94.4% vs. 101.9%, p = 0.01) compared to term-born children. We found a significant association between the variability of neonatal tidal volume and effective airway resistance at age 6 (β = −0.34, p = 0.03). No association between neonatal FeNO or TBFVL and respiratory morbidity at 6-year follow-up was shown. Conclusion: Children born moderate to late preterm had lower lung function at age 6 than term-born children. We did not find evidence for the use of neonatal tidal breathing parameters as a predictor for subsequent respiratory morbidity or lung function, however sample size was small.