Canopy surface conductances of a spruce forest in the Solling hills (Central Germany) were derived from LE and H fluxes measured (by eddy correlation technique and the Bowen ratio method) and modelled (by an one-dimensional non-steady-state SVAT model (SLODSVAT)) using a rearranged Penman-Monteith equation ( Big-leaf approximation) during June 1996. They were compared with canopy stomatal conductances estimated by consecutive integrating the stomatal conductance of individual leaves over the whole canopy ( bottom-up approach) using SLODSVAT model.The results indicate a significant difference between the canopy surface conductances derived from measured and modelled fluxes ( top-down approach) and the canopy stomatal conductances modelled by the SLODSVAT ( bottom-up approach). This difference was influenced by some non-physiological factors within the forest canopy (e.g. aerodynamic and boundary layer resistances, radiation budget, evaporation from the forest understorey). In general, canopy surface conductances derived from measured and modelled fluxes exceeded canopy stomatal conductance during the whole modelled period. The contribution of the understorey's evapotranspiration to the total forest evapotranspiration was small (up to 5-9% of the total LE flux) and was not depended on total radiation balance of forest canopy. Ignoring contribution of the understorey's evapotranspiration resulted in an overestimation of the canopy surface conductance for a spruce forest up to 2 mm/s (up to 10-15%).