The annexation of Crimea in 2014 was a clear sign that Moscow is looking to extend its sphere of influence and it forced the Baltic States to take a very close look at their deterrent capabilities. The article introduces the basic concepts of deterrence and discusses the differences between the deterrent capabilities of Ukraine and the Baltic States. Furthermore, the threats that Russia presents, the factors that were responsible for Ukraine’s deterrence failure and the challenges that the Baltic States are facing are analysed. The article concludes that while the Baltic States are significantly better prepared for possible Russian aggression, their deterrent capabilities must continuously evolve to reflect the changes in the nature of modern warfare.