Over the past ten years disinformation has repeatedly been described as one of the greatest threats to democracy and has been the subject of much scholarly attention. Less attention has been given to how policymakers across the world have adopted a series of new counterdisinformation policies. These policies reshape the institutions governing democratic countries’ information spheres and therefore deserve more attention, especially because they are remarkably different. This prompts two questions: how do democratic states counter disinformation, and what leads them to opt for different policies to counter disinformation? To answer these questions, this thesis develops three theoretical arguments rooted in the main strands of IR 1) a self-defence argument, which claims that states develop counterdisinformation policies to defend themselves against ‘disinformation attacks’; 2) a party politics argument, which claims counter-disinformation policies are the product of party competition, and; 3) an information culture argument, which claims that frames within national information cultures lead policymakers to adopt different counter-disinformation policies. It then compares the explanatory value of the three arguments by applying them to three cases – the US, Sweden and Germany – which have taken different trajectories in countering disinformation. The comparative analysis systematically ‘asks’ a set of key questions for each case. These questions were deduced from each of the three theoretical arguments and relate to ‘pre-existing conditions’, policymakers’ reasoning, and the counter-disinformation policies’ design. The analysis relies on a broad variety of sources, including interviews with policymakers and reports on disinformation campaigns, while employing different qualitative methods, such as interviewing and a combination of deductive and inductive coding of policymaker statements. Ultimately, the thesis finds that multiple forces shape counter-disinformation policies at what can be understood as different stages in a funnel: at the entry stage, the degree of exposure to disinformation campaigns creates the impetus for states to react to disinformation, as policymakers experience a ‘perceptual shock’. At the middle stage of the funnel, the national information culture provides frames through which policymakers interpret disinformation, which also defines the scope of possible policy solutions. At the last stage, details about the policy design, such as issue linkages, are shaped by party political dynamics. When the policy has been adopted, it goes through a ‘feedback-loop’ that sends it back to be reshaped through the ‘funnelling process’ once again. As such, the funnel-shaped theory of counter-disinformation policies provides a new way to conceptualise the interaction between international and domestic variables, and shows that disinformation campaigns can lead to changes in national policymaking, both within and outside the traditional security policy domains.