Liquid-filled pores of Fischer-Tropsch catalyst lead to slow diffusion of the reactants and can cause internal transport limitations leading to a significant decrease of selectivity and productivity. As an approach to overcome these limitations, transport pores can be added to provide an additional pathway for mass transport. In this work, a 3D isothermal model was developed, which takes the effect of concentration gradients within the transport pores into account. A comparison with a 1D model showed, that a description by a 3D model is necessary for transport pores with diameters larger than 10 mu m.