["Recent evidence suggests that the exposure of children to their parents' smoking adversely effects endothelial function in adulthood. We investigated whether the association was also present with carotid intima-media thickness (IMT) up to 25 years later.", 'The study comprised participants from the Cardiovascular Risk in Young Finns Study (YFS, n = 2401) and the Childhood Determinants of Adult Health (CDAH, n = 1375) study. Exposure to parental smoking (none, one, or both) was assessed at baseline by questionnaire. B-mode ultrasound of the carotid artery determined IMT in adulthood. Linear regression on a pooled dataset accounting for the hierarchical data and potential confounders including age, sex, parental education, participant smoking, education, and adult cardiovascular risk factors was conducted. Carotid IMT in adulthood was greater in those exposed to both parents smoking than in those whose parents did not smoke [adjusted marginal means: 0.647 mm ± 0.022 (mean ± SE) vs. 0.632 mm ± 0.021, P = 0.004]. Having both parents smoke was associated with vascular age 3.3 years greater at follow-up than having neither parent smoke. The effect was independent of participant smoking at baseline and follow-up and other confounders and was uniform across categories of age, sex, adult smoking status, and cohort.'] Is exposure to parental smoking in childhood or adolescence associated with increased carotid intima-media thickness in young adults : evidence from the Cardiovascular Risk in Young Finns study and the Childhood Determinants of Adult Health Study?