Interaction between orchids and fungi belongs to little understood aspects of orchid biology. This thesis investigated an identity of mycorrhizal and other fungal symbionts of several European orchid species and also an influence of these fungal symbionts on ecology, distribution, and evolution of the studied orchid species. Diverse methodological approaches were used including in situ seed germination, culture-dependent and -independent techniques for fungal isolation and identification, molecular phylogenetics, stable isotope analyses, and transmission electron microscopy.