Deadwood is an important component of the forest ecosystem and represents a central input for carbon storage studies. In addition to information on the presence of deadwood, the volume or biomass as well as the degree of decay are of interest. Usually, deadwood is surveyed in the context of forest inventories at plot level, whereby the lying as well as the standing deadwood is recorded by means of diameter at breast height, and tree height and stem length respectively. Another method is the line-intersect sampling (LIS), where all lying trunks intersecting with a line are recorded. Finally, statistical methods can be used to estimate the total amount of deadwood in a defined area. Due to the rapid developments in the field of UAV-LiDAR, it is now possible to acquire 3D point clouds with a very high point density even for larger survey areas at favourable prices. This makes it possible to determine the deadwood for large areas. The lying deadwood is detected and its volume is estimated from UAV-LiDAR and image data (RIEGL-VUX-120, PhaseOne-iXM100) data with a point density of >4000 pts/m² for the Rohrach natural forest reserve with an area of 48 ha. From the aerial images a true-orthopoto is calculated with a pixel size of 5 cm. Voxel-based approaches are used which take into account not only the geometrical properties but also the radiometric properties of the backscattering objects. The results are compared with reference surveys of 48 plots (437 trees) and with LIS (174 trees). The results show a very high completeness of the detected deadwood. The validation with the plot-based deadwood volumes shows high accuracies. The total deadwood volume for the entire area show some deviations which have to be analysed in more detail in the next months. This study is funded via the Austrian Waldfonds.