Biodiversity is the diversity of life forms on earth manifesting itself at the species, ecological and genetic levels. This concept includes diversity of species, biocenoses, landscapes, ecosystems and genes. Biodiversity is a factor shaping the biosphere, ensuring the normal functioning of the natural environment and directly influencing human living conditions. Sustaining biodiversity is the most basic task of the environmental protection, both at the local and at the international level The Carpathian Mountains are the Europe’s largest mountain range (approx. 1,500 km across seven countries) and a natural treasure of global significance. They support Europe’s largest remaining area of virgin forest, many endemic species of plants and significant populations of brown bears, wolfs, lynx etc. A rich cultural heritage reflects centuries of human settlement and history. The actual profound social and political change faces this area with unprecedented challenges. According to the  Millennium ecosystem Assessment, the total number of species of the Earth ranges from five to 30 million, and only about 2 million species have been formally identified. Knowledge of World fauna is unevenly balanced (and in the Carpathians also). The known number of species is highly biased in favour of the larger, more charismatic plants and animals, notably  vertebrate animals and vascular plants. Taxonomic groups of which individuals are easily observable, well-known and admired species ,  variously called „flagship”, „charismatic”, „iconic”, economically significant  or practical significators for the nature conservation  are subject to sustained scientific attention,  and they receive the “lion’s share” of public and private financial support, publicity, research, awareness of the protective legislation. Most of the world’s species at risk of extinction are neither particularly attractive nor obviously useful, and consequently lack conservation support.  We have to be aware that in the majority of cases biodiversity, defined in such a way, is in some sense “virtual” as it depends on the degree of fauna research, and in the case of many ecosystems it leaves much to be desired. A good example of close relation between “virtual” and “Real”  biodiversity are bats. In this case, the “Virtual” biodiversity is close to the “Real” ones (Wołoszyn, 2012). Between 53 european bat species a number of 33 are reported from the Carpathian Mts. This means about 70% of whole bat fauna of Europe. Recent bat fauna in the area North of the Carpathians (Southern Poland) consists of 25 bat species, meaning about 55% of whole European bat fauna and 78% of bat fauna of the South Carpathians Mountains.. The most commonly considered facet of biodiversity is species richness  - the number of species in a site. Diversity index at the α-level  (Margalef’s  Index) is higher if, at the comparable species number, the number of individuals is lower. The similarity of hibernating bat fauna in the Southern Carpathians and in the Beskidy Mountains in Poland at β-level of diversity is low – lost from 0.28 to 0.030. Similarity of bat hibernating fauna in the Southern Carpathians is higher and equal to 0.50. It corresponds to the geographycal gradient of bat distribution in the Carpathian Mts. The significant difference can be observed between bat fauna during hibernation and summer periods of activities. As an example, St. Grigore Decapolitul cave (in Southern Carpathians - Romania) was inhabited by bats during the summer and winter periods. Jackard Index is very low (0.25). In case of bats, because of their behaviour which they use in different biotopes during summer activity, transitory and hibernating periods, the standard methods of evaluation of both Alpha and Beta diversity are not comparable. we must find new standards for quantitative evaluation of diversity of bat fauna during different periods of their activities. conclusions. In the light of the Convention on Biological Diversity, its protection, and the sustainable use of its components, are strictly related and complementary notions. The most crucial feature of this approach is that it ensures the conservation of the natural environment as a whole, which includes rich and diverse ecosystems, poor ecosystems, and those at different stages of ecological succession as well as components that have been so far unappreciated or even deliberately destroyed. And above all, it is necessary to give more attention to the basic study in the field of systematics and distribution of plants and animals for to get a basic information on the changes of biodiversity in a longer periods.