The article states that war is perhaps the most potent catalyst for bringing societal issues to the front and revealing gaps in legislation that require not only prompt but also efficient responses from legislators. Thus, the majority of criminal law issues related to investigating and countering collaborationist activities remain unresolved and demand thorough investigation and coverage. It is pointed out that criminalizing collaborationist activities amidst the Russian-Ukrainian war is a necessary criminal law measure to punish a person (citizens of Ukraine) for unlawful actions in favor of the enemy (aggressor) state and to the detriment of our country. Criminalized actions which by their content are manifested in collaborationist activities (a new Article 111(1) of the CC of Ukraine) are akin to actions that, according to Article 111 of the CC of Ukraine, should be considered high treason. However, it should be taken into account that one of the differentiating features of the elements of these crimes is the period of an act: before occupation of territory: it is regarded as high treason; after occupation: it is collaborationism. It is noted that the new legal constructs of the elements of crimes against national security in Articles 111 (High Treason), 111(1) (Collaborationist Activities), 111(2) (Aiding the Aggressor state) of the Criminal Code of Ukraine raise many questions regarding their differentiation. The paper outlines the expediency of differentiating such collaborationist activities as transferring material resources and aiding the aggressor state. The latter encompasses voluntary collection, preparation, and transfer of material resources or other assets to representatives of the aggressor state, its armed formations, or the occupation administration of the aggressor state based on whether material resources are in possession of a person or not. It has been determined that in cases where any crime envisaged in Parts 1-8 of Article 111(1) of the Criminal Code of Ukraine was interrupted at the stage of preparation or attempt, and there was voluntary renunciation, the person is not subject to criminal liability (except in situations where actions actually committed by this person contain elements of another criminal offense). It has been proven that collaboration with the invader must receive appropriate legal assessment, and persons who have committed such crimes should be held criminally liable for collaborationist activities.