Background Since 2005, the international guidelines for out-of-hospital cardiac arrest (OHCA) use puberty to differentiate paediatric and adult care. This threshold is mainly relied on the more frequent respiratory aetiologies in children. Hitherto, to the best of our knowledge, no study has compared the characteristics and outcomes of non-pubescent children, adolescents and adult patients with OHCA. In this study, we intended to describe the characteristics, outcome and factors associated with survival of patients who experienced OHCA in the three groups: children, adolescents (pubescent<18 years) and adults (<65 years), to assess the pertinence of the guidelines. Methods Data from the French national cardiac arrest registry (2012–2017) were used in this nationwide observational study. Victims of OHCA who were <65 years old were included. The characteristics and outcomes of children and adolescents, and adolescents and adults were compared. Logistic regression was performed in each group to identify factors associated with survival at day 30. Results We included 934 children, 433 adolescents and 26 952 adults. Respiratory aetiology was more frequent and shockable rhythm less frequent in children compared with adolescents (25.5% vs 17.2%, p=0.025 and 2.4% vs 6.8%, p<0.001, respectively). However, these differences were not observed between adolescents and adults (17.2% vs 14.1%, p=0.266 and 6.8% vs 10%, p=0.055, respectively). Between children and adolescents, and adolescents and adults, there was no significant difference in survival at day 30 (8.6%vs 9.8% and 9.8% vs 8.5%, respectively). For all groups, shockable initial rhythm was a factor of survival. Conclusion Frequency of respiratory aetiologies and shockable rhythm were common in adolescents and adults and different between children and adolescents. These results indicate that puberty as a threshold in international guidelines seems to be relevant.