The article is devoted to the analysis of the mutual influence and interrelationship of two European security challenges – the unresolved protracted conflicts in the post-Soviet space and the conventional arms control (CAC) in Europe. The impossibility to account for and verify arms in the conflict “grey zones”, creating local exceptions from this regime, has led to the fact that the problem of unsettled protracted conflicts has always remained on the agenda of the modern CAC regime in Europe since the early 1990s. However, over the past three decades, the dynamics of their mutual influence have gradually changed. The author identifies three conditional stages in the development of this process. At the first stage, in the 1990s, unresolved conflicts proved to be one of the major problems for the renewed and emerging CAC regime in Europe; nevertheless, the dynamics of its development were positive overall. At the second stage – in the 2000s – when the need for the regime transformation increased, conflicts became a significant obstacle to its reform and it went into a state of stagnation. Finally, since the late 2000s, with the development of erosion processes in the CAC regime itself, when its key mechanisms, such as the CFE Treaty, became ineffective, the European security system climate has deteriorated and the protracted conflicts proved increasingly difficult to resolve. That is, if at first conflicts were a problem for the CAC regime, then the opposite effect has emerged and the crisis of the regime itself has started to affect the resolution of conflicts. Besides, already under the conditions of the CAC regime degradation and the general crisis of the European security, a new serious conflict has started in Ukraine, which later entered a protracted phase, including due to the loss of trust and the impossibility to organize arms control on the territory of the conflict. Paradoxically enough, arms control has proven to be ineffective and inoperative exactly where it is needed most – in conflict regions. As a result, such exceptions in the CAC have undermined this regime from the very beginning, and with the Ukrainian conflict they have become even more numerous. The arms control regime main function of reducing tension and maintaining military and political stability has been impaired. To overcome this systemic crisis, comprehensive solutions are needed to provide for the arms control even in protracted conflicts and mitigate the contradictions around their unresolved status, for example, in the form of a status-neutral arms control.