The authors regret that there was an error in their review article. They have been informed that information cited in this review about the Meyer et al. [17] results for liverworts and hornworts, which are discussed thoroughly in Section 2 of this review, were erroneous by 3 orders of magnitude due to a typographical error in the original publication, and the estimated conductances are actually in the mmol m−2 s−1 range (pers. comm. Howard Griffiths to David Hanson, July 25, 2012). As a consequence, the paragraph on p. 72 beginning: “In the case of hornworts and liverworts, estimates of gm are five orders of magnitude smaller than for spermatophytes (Fig. 1 inset)” is not valid, except for the sentence stating that “this strongly suggests the occurrence of an evolutionary trend towards higher gm, although knowledge of gm values of intermediate groups – i.e. mosses and ferns – may be necessary to confirm such a trend”. Moreover, the inset to Fig. 1 describing these data are not valid and thus Fig. 1 should appear as follows: (voir PDF) Corrigendum, volume 196, November 2012, pages 31, doi: 10.1016/j.plantsci.2012.08.001 ; Mesophyll diffusion conductance to CO2 is a key photosynthetic trait that has been studied intensively in the past years. The intention of the present review is to update knowledge of g(m), and highlight the important unknown and controversial aspects that require future work. The photosynthetic limitation imposed by mesophyll conductance is large, and under certain conditions can be the most significant photosynthetic limitation. New evidence shows that anatomical traits, such as cell wall thickness and chloroplast distribution are amongst the stronger determinants of mesophyll conductance, although rapid variations in response to environmental changes might be regulated by other factors such as aquaporin conductance. Gaps in knowledge that should be research priorities for the near future include: how different is mesophyll conductance among phylogenetically distant groups and how has it evolved? Can mesophyll conductance be uncoupled from regulation of the water path? What are the main drivers of mesophyll conductance? The need for mechanistic and phenomenological models of mesophyll conductance and its incorporation in process-based photosynthesis models is also highlighted.