Disinformation is one of the most significant problems of modern societies. Its mechanisms and effects, as well as possible ways to counteract it, are of interest to various institutions. The book presents reflections based on disinformation research conducted within the Central European Digital Media Observatory. The authors represent different research approaches and use different methodologies. Thanks to this, we were able to present an in-depth and multithreaded picture of disinformation, both from the perspective of its actors, structures and impact on the audience. The texts deal with the most significant crises of recent years, which contributed to the strengthening of disinformation tendencies, such as the Covid-19 pandemic or Russia’s aggression in Ukraine.