Among the protected sites of the Eastern Carpathians, the Synevyr National Nature Park (NNP) in the Zakarpattia region of Ukraine is one of the most valuable and was created to preserve its unique mountain beech and spruce forest communities. The importance of the conservation of typical natural virgin forest ecosystems of the Central European mountain systemis emphasized. The aim of this article was to determine the state of the naturalness of virgin forests in the territory of Synevyr NNP, to analyse their syntaxonomy, and to establish the floristic and geobotanical characteristics of its virgin forests and to distinguish the existing biodiversity threats. It was established that the studied plots of beech and spruce forests within the territory of the Synevyr NNP have a distinct virgin nature based on their structure, forest valuation parameters, spontaneous dynamics and other features. Syntaxonomically the virgin forests of the park belong to two associations: