INTRODUCTION: The tobacco industry (TI) has used small cigarette pack sizes to encourage brand-switching and consumption, and to mitigate the impacts of tobacco tax increases. Since 2016, the European Union (EU) Tobacco Products Directive (TPD) specifies a minimum pack size of 20 cigarettes. We examined cigarette pack sizes in the EU and whether pack size composition differed between cheap and expensive price segments, as well as the impact of the revised TPD. METHODS: We conducted a longitudinal analysis of pricing data from 23 EU countries between 2006-2017. We examined pack sizes over time to assess the impact of the TPD, differences in pack size composition between cheap and expensive price segments, and compared gaps in median prices between products using actual and 'expected' prices (price if all packs contained 20 sticks). RESULTS: Cigarette pack sizes changed over time, across the EU. The distribution of pack sizes varied between price segments, with small pack sizes especially frequent in the cheap segment of the cigarette market, but this varied over time and across countries. Packs of <20 cigarettes almost disappeared from the data samples after implementation of the TPD. CONCLUSION: Implementation of the TPD appears to have virtually eliminated packs with <20 cigarettes, restricting their use by the TI. Our analysis suggests pack sizes have been used differentially across the EU. Country-level analyses on the industry's use of pack sizes, consumer responses, and evaluations of restricting certain pack sizes are needed to confirm our findings and strengthen policy.