Effective management of tree-hollow-dependent wildlife is enhanced by detailed knowledge of the trees used for shelter and breeding. We describe the characteristics of 52 den trees and hollows (cavities) used by the yellow-bellied glider (Petaurus australis) in the south-west of its geographic range. We compared the following attributes of den trees to reference trees: tree height, diameter at breast height, hollow entrance height, hollow entrance diameter, cavity diameter, cavity depth, cavity roof height and cavity wall thickness. Dens and reference trees showed a highly significant multivariate difference (P < 0.001), with these variables explaining 64% of the variance. Univariate analyses revealed that hollow entrance height was significantly different between den trees (9.0 ± 0.5 m) and reference trees (5.5 ± 0.3 m). While not significant, den trees tended to have narrower hollow entrances, deeper cavities and thinner walls than reference trees; cavities used by yellow-bellied gliders, on average, measured 36.8 cm deep and 18.0 cm in diameter, and had entrances 10.6 cm in diameter. These observations should assist forest management for this species.