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Mesophyll resistance to CO 2 diffusion (r m ) and the maximum carboxylation rate of Rubisco (V cmax ) affect photosynthetic rates, and can potentially also influence the percentage of respiratory and photorespiratory CO 2 being refixated (P r ) by mesophyll cells. Here we investigated how various leaf anatomical traits (e.g. leaf mass per area [LMA] and leaf dry matter content [LDMC]) influenced r m in leaves of mature forest trees. We further explored how r m and V cmax in turn affected P r , and if these traits varied among species and leaves along a light gradient. Photosynthetic CO 2 response of leaves grown in high-, medium-, and low-light environments was measured, from Pinus sylvestris [Scots pine], Picea abies [Norway spruce], Quercus robur [English oak], and Betula pendula [Silver birch] in southern Sweden. A modified version of the Farquhar-von Caemmerer-Berry model was fitted to the leaf gas exchange data to estimate V cmax , r m and P r . We found that of all leaf traits measured, only LMA for Q. robur was significantly higher in leaves from high-light environments. When comparing species, both r m and LMA were significantly higher in the conifers, and r m had a negative correlation with V cmax . We found that P r was similar between different species and functional groups, with an average of 73.2% (and SD of ±10.4) across all species. There was a strong, positive correlation between P r and V cmax in broadleaves, and we hypothesise that this effect might derive from a higher CO 2 drawdown near Rubisco in leaves with high V cmax ., (Copyright © 2020 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)