PURPOSE OF REVIEW: Early stage lung disease has long been synonymous with infancy and childhood. As diagnosis happens earlier and conventional management improves, we are seeing larger proportions of people with cystic fibrosis (CF) in adolescence and even adulthood with well preserved lung health. The availability of highly effective cystic fibrosis transmembrane conductance regulator modulator drugs for a large proportion of the CF population will impact even further. Transitioning into adult care with 'normal' lung function will become more common. However, it is crucial that we are not blasé about this phase, which sets the scene for future lung health. It is well recognized that lung function assessed by spirometry is insensitive to 'early' changes occurring in the distal, small airways. Much of our learning has come from studies in infants and young children, which have allowed assessment and optimization of alternative forms of monitoring. RECENT FINDINGS: Here, as a group of paediatric and adult CF specialists, we review the evidence base for sensitive physiological testing based on multibreath washout, lung imaging, exercise and activity monitoring, assessment of infection and quality of life measures. SUMMARY: We seek to emphasise the importance of further work in these areas, as outcome measures become widely applicable to a growing CF population.