Bechstein's bat (Myotis bechsteinii) is a European species, restricted to woodlands with preference for mature deciduous forests in lowlands. It is considered rare throughout its range, although it may be common in optimal habitats. Roosts play crucial roles in the ecology of bats, and survival is partially dependant on the extent to which roosts protect bats from environmental extremes and predators. Roost selection is especially important for reproductive females, due to the higher energetic demands imposed by reproduction so understanding roost selection by maternity colonies is important for conservation. We investigated maternity roost selection by M. bechsteinii in southwestern Spain as a hierarchical process that proceeds from broad landscape scales to fine-scale local habitat characteristics. Radio-tracking of 28 lactating females allowed location and census of 13 maternity roost sites. Roosts were characterised at four detail scales (cavity, tree, stand, and landscape). All the roosts occurred in Quercus pyrenaica trees, within stands of the same species of very diverse structure. Ten of the roosts were former woodpecker holes, among which seven had their entrance modified by nuthatch. Roosts were located inside the forest and close (< 620 m) to permanent water sources. Roost trees were characterised by a higher proportion of dead branches. Other explored variables such as tree height, orientation, foliar cover, and elevation did not explain distribution of roosts at any scale. The species' breeding roost selection is described for the first time in a Mediterranean area.