Check-list of vascular flora of the Irkutsk Region published in 2008, compiled information about diversity of plant species in the region. In current article we publish the summary table containing information about size, floristic richness and specificity of all regional divisions used in the Check-list for detailing distribution of species. The regional division “Пю-6” we used as an example showing, that even short floristic investigations can play important role in increasing of our knowledge about floristic diversity of weekly studies regions. During several days of August of 2012 we revealed 103 vascular plant species missed in the Check-list for the “Пю-6”. Among majority species common for the Region, there are comparatively rare ones, i.e. Aconogonon divaricatum (L.) Nakai ex Mori and Allium senescens L. Plantago salsa Pall. is the first finding for the broader region “Пю”.