The European red click beetle, Elater ferrugineus L., is associated with wood mould in old hollow deciduous tree. As a result of severe habitat fragmentation caused by human disturbance, it is threatened throughout its distribution range. A new odour-based trapping method, which is very efficient in attracting males, was used in the present study to relate the occurrence of E. ferrugineus to the density of deciduous trees using a recently completed regional survey recording >120, 000 deciduous trees. Results showed that the occurrence of E. ferrugineus increased with increasing amount of large hollow and large non-hollow trees in the surrounding landscape. Quercus robur was found as an important substrate for E. ferrugineus and two groups of tree species (Carpinus betulus, Fagus sylvatica, Ulmus glabra, vs. Acer platanoides, Aesculus hippocastanum, Fraxinus excelsior and Tilia cordata) could be a complement to the existence of Quercus in sustaining the beetle’s population. E. ferrugineus responded to the density of Quercus at two different spatial scales, 327 m and 4658 m, suggesting that a multi-scale approach is important for studying the species. In conclusion, for conservation management, priority should be given to Quercus, and also to all deciduous trees in the genera listed above, regardless of the tree quality. The response showed by E. ferrugineus on the amount of substrate at two different scales indicates that using multi-scale approach in studying this particular species is the better option as single-scale approach may result in poor decision support.