Changes in the species composition and structure of high-mountain vegetation of the Urals are described and characterized in connection with the introduction of Juniperus sibirica. About 60 plots (relevés) of mountain tundra communities were studied in the Northern Urals: Zyryanovka Mountain (N60°57ʹ, E58°58ʹ); Kvarkush Ridge (N60°08ʹ, E58°44ʹ), and the Southern Urals: Northern Nurgush Mountain (N54°48ʹ, E59°08ʹ); Poperechnaya Mountain (N54°39ʹ, E58°39ʹ). Common geobotanical methods were used. Study plots were chosen to represent different abundances of J. sibirica. The structure of tundra plant communities dominated by J. sibirica departs from other groups of plant communities in the dendrogram. Tundra areas without J. sibirica or where its contribution was up to 30–40 % did not have any regularity in the distribution. Changes in the ratio of vascular plant ecological and coenotic groups were measured, showing significant differences between Northern and Southern Urals. Northern Urals: on Zyryanovka Mountain a significant increase happened in the percentage cover of mesophytes, while on the Kvarkush Ridge the percentage cover of psychrophytes declined greatly. Southern Urals: the percentage cover of mesophytes declined significantly on Mt. Nurgush. The ratio of coenotic groups of vascular plants in the mountain-tundra communities changed the most notably in the Northern Urals: on Mt. Zyryanovka the percentage cover of marginal tree species significantly increased while the percentage cover of high-mountain species decreased; the Kvarkush Ridge experienced a significant decline in the percentage cover of high-mountain species. Data about vascular plants species common for tundra communities in the Northern and Southern Urals, and about the composition of endemic and relict species are presented.