The Parsnip River area in British Columbia (BC), Canada, provides important habitat for grizzly bears (Ursus arctos). This area contains 2 adjacent topographic regions: (1) a relatively pristine portion of the Hart Ranges of the Canadian Rocky Mountains, and (2) a plateau on which timber harvests have occurred. Increasing human modification of both landscapes may affect the quality of grizzly bear habitat. Therefore, we examined denning behavior and den-site selection of grizzly bears in this area based on data from 61 grizzly bears radiocollared between 1997 and 2002 (34 plateau, 27 mountain bears). Adult females residing in the mountainous landscape arrived earlier to their denning areas (14 Oct versus 26 Oct), entered dens earlier (23 Oct versus 9 Nov), and emerged later (11 May versus 24 Apr) than plateau females, spending on average 36 days longer in their dens (200 days versus 164 days). Dens used in consecutive years by mountain females tended to be closer to one another (x̄ = 2.4 km) than those of plateau females (x̄ = 5.1 km). Dens in the mountains were excavations into sloping ground (74%), or natural caves (26%), using rocks as the primary stabilizing structure (47%). Resource selection functions (RSF) revealed that mountain grizzly bears selected dens in alpine habitats at mid-to-upper elevations. Plateau bears mainly excavated dens under the base of trees (90%), where roots stabilized material (80%). These dens primarily were located in older-aged forest stands ranging from 45–99 years (40%) or >100 years (50%); RSFs further revealed that grizzly bears on the plateau selected stands with tall trees. Plateau dens also were located away from roads, possibly because of less disturbance and because older trees were farther from roads.