Anthropogenic fragmentation of natural landscape takes on a global character. An increasing degree of the anthropogenic fragmentation undermines stability and reduces productivity of ecosystems all over the world. Index of landscape fragmentation (meff) was used for realization of idea on evaluation of the degree of landscape fragmentation and its effective mesh size on the example of 17 nature-protected areas in the Western Ukraine. Railways, hard surface roads and completely built-up areas were the factors considered to cause landscape fragmentation. On the basis of our survey, we found out that total size of a protected area is not the main criterion of its effectiveness for biodiversity conservation, and high degree of landscape fragmentation has a significant negative impact on index of landscape fragmentation. Besides, not only the degree but also the pattern of fragmentation has a significant influence on the effective mesh size. Taking into account the negative effects of landscape fragmentation as one of the threats for biodiversity on the territory of protected sites, we consider a possibility of combining the adjacent areas of Roztochchia NR and Yavorivskyi NNP in order to reduce the fragmentation degree and increase the effective mesh size.