In this paper we show a detailed verification of an analytical thermal diffusivity model using finite element simulations. The real pore morphology for the simulation models are obtained by computed tomography measurements. The heat transfer by conduction is simulated in transient analyses. The thermal diffusivity values are calculated from the temperature field on the front (reflection mode) and on the back sides (transmission mode). Investigations show that the analytical model correlates well with the thermal diffusivity values calculated in transmission mode. Furthermore, the simulations show a discrepancy in the reflection mode measurements due to the stronger influence of the pore morphology. These findings are similar to those seen in pulsed thermography experiments. In conclusion, the analytical thermal diffusivity model allows a precise quantification of porosity in carbon fiber reinforced polymer structures using transmission mode measurements.