The effect of shear deformation and rotatory inertia should be taken into account in modeling Lamb waves in composite laminates. However, the first and second-order shear deformation plate theories which do not satisfy the stress free boundary condition are uneconomic approximations, because one has to develop a complicated scheme to compute the shear correction factors. The stress free boundary condition requires an in-plane displacement field expanded at least as cubic functions of the thickness coordinate. Hence, in this paper, the dispersive curves of Lamb waves in laminates are calculated according to two new third-order shear deformation plate theories, considering the stress free boundary condition. The lower anti-symmetric Lamb mode results of the new theories are closest to the exact solutions from 3D elasticity theory, when compared to several existing plate theories.