Five-year longitudinal data on a cohort of early to middle adolescents (N = 923) and a cohort of middle to late adolescents (N = 390) were used to examine the correlates of hypermaturity (i.e. 12-year-olds with a personality profile resembling the profile of an average 20-year-old) and immaturity (i.e. 20-year-olds with a personality profile resembling the profile of an average 12-year-old) of personality. Analyses revealed that girls with high levels of hypermaturity exhibited high levels of internalizing problem behaviour and conflict with parents, while hypermaturity in boys was only associated with internalizing problems. Immature girls had low levels of anxiety and high levels of minor delinquency, whereas immature boys reported low levels of anxiety and high levels of physical maturity. These findings suggest that off-time personality development is an interesting concept deserving further exploration.