INTRODUCTION: Alcohol consumption poses a significant health risk, contributing to 10% of deaths in the WHO European Region. To combat this, the WHO recommends the implementation of its 'best buy' policies-three cost-effective alcohol policies that include higher taxes, restricted availability and marketing bans. While evidence links alcohol marketing to increased consumption, the effectiveness of marketing bans in decreasing alcohol use remains inconclusive. Lithuania's 2018 comprehensive alcohol marketing ban offers a unique opportunity to measure the impact of this particular 'best buy' control policy. METHODS AND ANALYSIS: We will analyse repeated cross-sectional measures of alcohol use among 15-year-old and 16-year-old adolescents from Lithuania and other five European Union countries (Estonia, France, Italy, Latvia and Poland). Data from the European School Survey Project on Alcohol and Other Drugs collected between 2003 and 2019 will be used, as well as longitudinal alcohol policy data meticulously gathered through official records, supplemented by relevant literature and consultations with national authorities. Although all six countries introduced best buy alcohol policies-primarily via excise tax increases implemented at different times-only Lithuania implemented a full marketing ban. Generalised linear mixed models will be employed to assess the impact of national alcohol marketing restrictions on alcohol consumption, controlling for participant characteristics, social behaviours and country-level variables such as other alcohol control policies evaluated through a partial Bridging the Gap (BtG) scale. Sensitivity analyses will explore different outcome time periods and model specifications. ETHICS AND DISSEMINATION: The Research Ethics Board of the primary recipient of the grant has approved the secondary data analyses as outlined in the grant proposal (CAMH REB 050/2020 delegated review, renewed annually). The study results will be published in a peer-reviewed journal, presented at conferences, and shared with policymakers.