Background: An estimated 8 million people die every year due to tobacco use. The COVID-19 pandemic has increased the health costs 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. Methods: Using 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. Within smokers, we separately estimate effects for occasional smokers and regular smokers. Results: We find large, sustained, decreases in tobacco consumption during COVID-19. We estimate that, controlling for price, weekly tobacco purchase rates decline by 24 percent and average quantities decline by 12 percent 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 non-smokers or occasional smokers. Among regular smokers, purchase rates decline by about 30 percent, tobacco consumption declines by about 20 percent and quitting rates increase by about 10 percentage points. Conclusion: Our results are consistent with individuals responding to the increased health risks of smoking due to COVID-19 and suggest that the pandemic could lead to sustained reductions in tobacco consumption.