Fine root and ectomycorrhizal root density and biomass were quantified in 2003 and 2004 by sequential soil coring in a 54-year old second-growth stand and 3- and 14-year-old third-growth stands of Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) at Fluxnet–Canada research sites on east–central Vancouver Island, British Columbia. We investigated the relationships of fine root mass and carbon concentration (%C) with soil depth, stand age, and soil substrate. Fine root %C varied significantly with stand age, was lower in the forest floor (LFH) and deeper mineral soil than in shallow soil horizons, and was lower for ectomycorrhizal (EM) versus non-EM roots. These results suggest that differences in root %C associated with soil depth and forest stage should be accounted for when scaling root data for carbon (C) budgets. Total fine root density (mass/soil volume) in the LFH was highest in the 54-year-old stand and declined with depth in mineral soil; whereas total, live, and live conifer root density in the mineral soil was generally highest in the 14-year-old stand, intermediate in the 54-year-old stand, and lowest in the 3-year-old stand. Ectomycorrhizal fine root density was highest in the 54-year-old stand, intermediate in the 14-year-old stand, and lowest in the 3-year-old stand; especially so in the LFH and shallowest mineral soil. Total fine root biomass (mass/area) generally increased with stand age in the LFH, but patterns were less definite in mineral soil. When the LFH and mineral soil were combined, total fine root biomass was lowest in the 3-year-old and highest in the 14- and 54-year-old stands. Ectomycorrhizal fine root biomass was significantly higher in the 54-year-old than in either the 14- or 3-year-old stands. The higher fine root biomass in the 14-year-old stand was unexpected; however, the higher EM root biomass in the 54-year-old stand suggests that a greater proportion of carbon is allocated to the ephemeral absorptive structures of the EM fungi in forests at this age.