The aim of the study was to assess lung function longitudinally after neonatal extracorporeal membrane oxygenation (ECMO), and to identify any effects of diagnosis and perinatal characteristics.121 neonatal ECMO-treated children (70 with meconium aspiration syndrome, 20 congenital diaphragmatic hernia and 31 with other diagnoses) performed a total of 191 lung function measurements at 5, 8 and/or 12 yrs. We assessed dynamic and static lung volumes, reversibility of airway obstruction and diffusion capacity.Mean SDS forced expiratory volume in 1 s (FEV1) at 5 yrs before and after bronchodilation (-0.51 and 0.07) was significantly higher than at 8 (-0.79 and -0.4; p,0.04) and 12 yrs (-1.10 and -0.52; p,0.003). Mean SDS for all spirometric parameters before and after bronchodilation were significantly lower in the congenital diaphragmatic hernia group compared with the other diagnostic groups (all pf0.025). A significant volume of trapped air was observed in 86% patients with congenital diaphragmatic hernia, 50% with meconium aspiration syndrome and 58% with other diagnoses. After bronchodilation, mean SDS FEV1 and forced vital capacity were negatively influenced by duration of ventilation (both p,0.001) and duration of ECMO (p50.003 and p50.02, respectively).Long-term pulmonary sequelae after neonatal ECMO-treatment mainly occur in congenital diaphragmatic hernia patients and tend to deteriorate over time.