BackgroundAn estimated 8 million people die every year due to tobacco use. The COVID-19 pandemic has increased the health consequences of smoking, which is a leading risk factor for more severe COVID-19 symptoms, hospitalization, and death. The pandemic has also led to reductions in physical activity, increases in stress and declines in mental well-being, all factors commonly associated with triggering higher tobacco use.MethodsUsing a longitudinal data set of purchasing behavior from 2019–2020 among a national sample of the Danish population (n = 4042), we estimate changes in tobacco use during the COVID-19 pandemic. Our analysis compares tobacco purchases prior to the pandemic to purchases during the pandemic, at the individual level. We also examine effects within subgroups based on smoking behavior in 2019 prior to the pandemic. We estimate effects for smokers and non-smokers and, within smokers, for occasional smokers and regular smokers.ResultsWe find large, sustained decreases in tobacco purchases during COVID-19. We estimate that weekly tobacco purchase rates decline by 24% and average quantities decline by 12% during the period spanning the onset of the pandemic in March 2020 through the end of the year. The declines are driven by regular smokers with little change in behavior among nonsmokers and increases in purchases among occasional smokers. Among regular smokers, purchase rates decline by about 30%, tobacco purchases decline by about 20% and quitting rates increase by about 10 percentage points.ConclusionsOur results suggest that the COVID-19 pandemic could lead to sustained reductions in smoking.