OBJECTIVES: To evaluate the impact of changes in cigarette taxes on smoking for youths aged 15-18 in Canada during the time of the Federal Tobacco Control Strategy (FTCS). METHODS: We used a difference-in-differences framework and leveraged the variation in cigarette taxes across Canada and over time. We used regression models with province and year fixed effects, and individual-level and provincial-level covariates on 2002-2012 data from the Canadian Tobacco Use Monitoring Survey. RESULTS: Tax increases generally did not affect smoking outcomes. Each increase of CAD $1.00 (adjusted to year 2000 dollars) in excise cigarette taxes per package of 20 was associated with a 0.2 percentage point (95% CI: -1.8; 2.2) change in smoking prevalence, and a change of 0.3 in mean cigarettes smoked in the past week (95% CI: -1.2; 1.8). CONCLUSION: From 2002 to 2012, smoking prevalence and mean smoking frequency were in steady decline among youths in Canada. This decline, however, was evident even among provinces with stable or decreasing cigarette tax levels. Tobacco taxes have mostly increased since the 1980s, and so, tax levels were already quite high by the launch of the FTCS. Province fixed effects and common temporal changes accounted for 83.7% of the variation in smoking prevalence. We derived similar results for smoking frequency. The cumulative tax increase during our study period was at least $1.00 for only three provinces. Thus, our findings suggest that factors driving down tobacco use among youths in all provinces appear to outweigh any impact of small tax increases at already high tax levels.