Populations of East-Asian species (Sсutellaria baicalensis, Sophora flavescens, and Astragalus membranaceus) in the territory of Zabaikaliye, the Russian Far-East and Inner Mongolia were studied. A total of 363 relevees were processed using the ecological scales, and ranges of environmental conditions were evaluated. To assess population optimum, the individual and cenopopulation features were taken into account. As the most appropriate, the ecological scales method proposed by I.A. Tsatsenkin et al. (1978) for analyzing forest-steppe communities was used. By integrating data on plant communities and populations the optimal conditions for each species were revealed. Generally, habitats of South and South-Eastern part of Zabaikaliye and the Russian Far-East are the most favorable for the species under study. We conclude that moisture might be the key factor for functioning of populations of East-Asian species.Key words: East-Asian species, Scutellaria, Sophora, Astragalus, distribution of plants, ecological gradients, ecological scales, population optimum, Zabaikaliye, Inner Mongolia.