Young adulthood is now considered a sensitive period in the progression of health inequalities over the life-course. This age group experiences highly dynamic and socially patterned life-course events that require nuanced modelling choices compared to those commonly used in public health sciences. To illustrate this, we estimate changes in the risk of smoking according to student status, employment status, living arrangements, and relationship status at different ages across education categories. We used longitudinal data in 1,243 young adults followed every two years between the ages of 18-19 and 24-25 in the Canadian National Population Health Survey (1994-95 to 2010-11). We examined the age-graded associations of occasional and daily smoking with educational attainment and transition statuses using random-effects multinomial logistic regression models with interaction terms. Post-secondary education, living with parents, studying, and being in a relationship were associated with a lower risk of daily smoking in main models, with some of these associations significantly varying in magnitude by age. The risk associated with living without parents at ages 18-19 disappeared by ages 24-25. Being single was both a protective factor at ages 18-19 and a risk factor at ages 24-25. Finally, the risk associated with being single was also stronger among those who did not pursue post-secondary education. These findings support the argument that the simple conceptualization of young adults’ circumstances – independent from age and social context – provides a limited understanding of the progression of health inequalities over the life-course. Research needs to consider the dynamic and intersecting nature of transition milestones during this intensive life period.Copyright © 2020 Elsevier Ltd. All rights reserved.