Aim: Extremely preterm birth, particularly before 24 weeks of gestational age (GA), is associated with complex health trajectories and lifelong support needs. This study aimed to estimate both medical and non-medical costs of illness in childhood for this population, while considering implications for person-centred and family-oriented care. Methods: We conducted a national, population-based register study including all children born <24 weeks GA in Sweden between 2007 and 2018 who survived beyond their first year. By linking health and social insurance registers, we assessed costs from a societal perspective, covering hospital care, pharmaceuticals, and social support. Results: Among 344 children (56% boys), the mean follow-up was 8.8 years. Expenditures were dominated by hospital-based care during infancy, while family-related and disability benefits became the major cost drivers thereafter. Children born at 21–22 weeks GA and boys showed more sustained non-medical costs compared with those born at 23 weeks GA and girls. Neonatal morbidities, including bronchopulmonary dysplasia, retinopathy of prematurity, and severe intraventricular haemorrhage, were linked to particularly high long-term support needs. Conclusion: Children surviving birth before 24 weeks GA contribute to substantial and enduring societal costs, shifting from acute medical care in early life to long-term social and family support. These findings underline the importance of person-centred approaches that extend beyond neonatal survival to encompass the lived realities of families. Early identification of needs, coordinated follow-up, and integrated care strategies may reduce fragmentation, support families in daily life, and promote more sustainable use of resources. Keywords: extremely preterm birth, person-centred care, health economics, societal costs