This thesis strives to raise and answer three questions about the concept of hybrid warfare: What concepts of hybrid warfare exist so far? How similar or different are they? How useful are they from conceptual standpoint? The questions are answered by a conceptual analysis consisting of survey of existing concepts, their comparison and detailed evaluation of two of them on the basis of criteria of conceptualization. The answers revealed several important issues of the concept. Firstly, there are too many different concepts of hybrid warfare, often formulated with insufficient care for previous debates and already established concepts. Secondly, the formulated concepts of hybrid warfare are often different to a degree, which calls into question the claim, that all of them are trying to capture the same phenomenon. Lastly, even the better elaborated of the hybrid warfare concepts seem to be rather poorly conceptualized and not very useful. These three answers together cast shadow of doubt on the currently popular concept of hybrid warfare. The results of this work call for more careful thinking on whether and how the use of this concept is helping or hurting both our understanding of contemporary conflicts and our defence efforts against contemporary threats.