The suitability of using K-theory to describe turbulent transfer within plant canopies was evaluated with field measurements and simulations of a detailed soil–plant–atmosphere model (Cupid). Simulated results with both K-theory and an analytical Lagrangian theory (L-theory) implemented in Cupid were evaluated against Bowen-ratio energy balance measurements and the temperature profiles in potato canopies. There was no difference between K- and L-theory in terms of simulating E, H and CO2 fluxes over the canopy. The model slightly underestimated measured E by 3–8%; the comparison of H contained much scatter and the model slightly overestimated CO2 flux. When the model was tested by simulating temperature and vapor pressure profiles within the canopy, the difference between the K- and L-theory was much smaller than the difference between each theory and the measurements. From simulated temperature profiles, the near-field correction provided by using L-theory seemed to be significant in canopies where the foliage is concentrated in the upper part, but appeared unnecessary for foliage distributed throughout the canopy depth. The major difference between K- and L-theory was in simulations of canopy radiometric temperature; with foliage distributed through out the depth of the canopy, K-theory consistently predicted higher canopy radiometric temperatures than L-theory by 2–8 °C, depending on leaf area index. More systematic study is required to determine if K-theory or L-theory is inadequate for remote sensing of radiometric temperature of canopies.