Résumé : The research topic of this dissertation is the use of astroturf lobbying in democratic societies. This tactic consists in creating fake grassroots movements for political purposes while keeping the real identity of the instigator secret. By lying about its true identity and by simulating citizen support for or against a political issue, this unethical strategy represents a threat to the well-being of democracy. For this reason, this study aims to shed light on astroturfing with two research objectives.The first objective aims to design a method to detect astroturf groups that are taking part in political debates. The method used for this purpose is a framing analysis. The underlying assumption is that astroturf groups frame an issue differently than genuine grassroots movements. The research design includes a quantitative text analysis of documents published by 72 interest groups active on the hydraulic fracturing debate in the United States. The method has successfully led to the identification of 12 astroturf groups.The second objective aims to assess the influence that astroturf groups have on public policy. For this purpose, the position papers of 31 interest groups active on the issue of hydraulic fracturing in the European Union have been analyzed with a similar quantitative method. One astroturf group has been identified from that analysis. To measure its influence, the evolution of the frames used in two reports voted by the European Parliament in 2012 have been studied with a correspondence analysis. The results show that the coalition of which the astroturf group is part was successful in influencing one of the two reports.The two case studies are insightful in understanding the role that astroturfing plays within broader lobbying strategies. Indeed, the findings of this study show that astroturf groups are spreading in the public sphere with the aim to deceive policymakers and public opinion in order to influence public policy.