['To investigate the associations between smoking in adolescence and adulthood, and changes in smoking behaviour between these age periods, with arterial stiffness in young adults; and whether any such associations could be explained by concomitant smoking-related levels of inflammation and endothelial dysfunction.', 'We studied 424 individuals (216 women) in whom smoking status was assessed in adolescence (age 15 years) and again in young adulthood (mean age of 22.6 ± 1.6 years), along with aorto-iliac, aorto-radial, and aorto-dorsalis pedis pulse wave velocity (PWV), and markers of inflammation (i.e. C-reactive protein and fibrinogen) and endothelial dysfunction (i.e. von Willebrand factor and tissue-plasminogen activator antigen) in young adulthood only.', 'Smoking in adolescence was associated with higher aorto-iliac PWV, as well as with inflammation and endothelial dysfunction levels (expressed as two scores), independently of other adolescent and adult lifestyles. Compared with never smokers, continuing smokers, but not starters nor quitters, showed higher aorto-iliac PWV, independent of changes in other lifestyle variables: +0.157 m/s (95% confidence interval 0.026-0.288). This difference was attenuated to 0.124 m/s (-0.009 to 0.257) after adjustment for changes in traditional biological risk factors, but was not materially affected when adjusted for the inflammation and endothelial dysfunction scores, despite the continuing smoking-related higher levels of inflammation and endothelial dysfunction. Smoking was not associated with aorto-radial and aorto-dorsalis pedis PWV.'] Is continuing smoking between adolescence and young adulthood associated with higher arterial stiffness in young adults : the Northern Ireland Young Hearts Project?