Background: In this article, the co-authors contribute to the development of Ukraine's criminal policy on the legal evaluation of collaboration with occupying forces, necessitated by the ongoing Russian Federation occupation of Ukrainian territory. The study, to some extent, continues the scientific discourse that was actualised after the addition of Article 111-1 to the Criminal Code of Ukraine. Its objective is to delineate the generic legal features of collaborationist activity, the responsibility for which was introduced in the Criminal Code of Ukraine in March 2022. By critically analysing the common features of collaboration with the occupier currently reflected in theory and practice, the authors develop a comprehensive vision of collaboration as a phenomenon distinct from high treason and related concepts. Methods: The research methodology employs a blend of general scientific methods of cognition (induction, deduction, analysis, synthesis, abstraction) and historical, linguistic and systemstructural research methods. The strategy focuses on identifying the features of collaboration with occupying forces, selecting the most typical and essential traits that differentiate it from related phenomena. Structurally, the article consists of two parts. The first part explores existing definitions of collaboration in literature and identifies the five most frequently mentioned features. The second part involves a detailed analysis of each feature to determine its suitability for characterising collaboration and distinguishing it from related concepts. At the same time, the features set forth in the current criminal law of Ukraine (lex lata) are compared against the perspective of the ideal model (lex ferenda). Results and conclusions: The phenomenon of collaboration with occupying forces has long been the subject of research by historians, while legal scholars traditionally examine it through the lens of high treason. However, establishing collaborationism as an independent crime in criminal law, along with high treason, requires its conceptualisation. This study demonstrates the impossibility of automatically transposing an array of effective historical research into the legal field. Criminal law requires clarity, unambiguity, and logic. At the same time, de lege lata, Ukrainian criminal law provides for a casuistic and eclectic set of features of collaborationist activity. Therefore, this article analyses each of the features that are commonly used to characterise collaborationism, aiming to improve the normative framework and formulate a clear concept that deserves to exist independently alongside the concept of high treason.