Tree hollows with wood mould constitute ecologically important structures in forest ecosystems that offer long-lasting microhabitats and nutritional resources for many endangered saproxylic arthropod species. Approximately 34% of all forest arthropod species in Germany are dependent on dead wood as a resource in at least one stage of their life cycle and can therefore be classified as saproxylic. Due to intensive timber harvesting and habitat loss many wood mould specialists are threatened because of their dependency on that specific habitat. We used emergence traps to collect saproxylic beetles from 52 tree hollows with wood mould in the Steigerwald region and 44 tree hollows in the Fichtelberg region in Bavaria, Germany, from the beginning of May to the end of August 2018. Over 200 saproxylic beetle species could be identified from 4,845 individuals (4,379 individuals in the Steigerwald and 466 in the Fichtelberg region). During the three-year study we will examine and compare the influence of forest and landscape structure on the diversity of saproxylic insects in tree hollows as well as the dispersal ability of selected species in a total of three forest regions. We will analyze different local parameters of the tree hollows as well as characteristics of the surrounding forest structure, like density of tree hollows, amount of dead wood, and tree species composition and their respective influence on saproxylic insect diversity inside the tree hollows. Subsequent population genetic analyses of selected species are expected to shed some light on the dispersal abilities of saproxylic insects with regard to landscape structure. Results of this study should help forestry authorities to develop more efficient conservation strategies concerning the preservation of highly endangered saproxylic insects in tree hollows.