An initial study of the interaction of Lamb waves with circular defects in plates is presented. The Lamb wave mode chosen for this paper was the S0 mode in the low frequency-thickness regime. The geometrical properties of this mode allow it to be analyzed using a 2D membrane finite element model which is computationally simpler than the alternative 3D case. A mesh was generated representing an area of the plate with a circular through-thickness hole. The reflection and scattering of an incident S0 wave at different monitoring angles are predicted showing that the scattered field contains the SH0 mode as well as S0. The amplitude of the reflected field is verified experimentally.