Occurrence of rare and pro-tected plant species is regarded as a strong argu-ment for creating a protected area. It is there-fore especially important to know whether rare and protected species are reliable indicators of abundance of other, more common, unprotected species. We analysed co-occurrence of protected and rare species with other xerothermic plant species in calcareous xeric grassland in West-ern Poland. In the years 2005–2006, on 62 plots (25 m 2 each) we identified vascular plants on a 60 km 2 area in the Odra R. Valley and its small-er tributaries valleys. Legally protected species appeared not to be better indicators of xerother-mic species richness than non-protected species. The rarest species (Anthericum liliago L., Carex supina Willd. ex Wahlenb. and Stipa borystheni-ca Klokov ex Prok.) were significantly less useful indicators of xerothermic species richness than other rare and common species. These results let us conclude that designing a network of pro-tected areas on the basis of rare and protected species may result that some common species, biodiversity hotspots or well developed phytoce-noses will be ignored.