In recent years composite materials are increasingly employed in a variety of aerospace applications because of its obvious merits. The present paper presents and discusses firstly the effect of the fibre orientations 0, bending-torsion material coupling, K on the eigenvalues and associated eigenvectors of a composite wing structure in a more realistic manner. The cantilevered composite wing structure is modeled in a way to simulate both Circumferentially Uniform Stiffness (CUS) and Circumferentially Asymmetric Stiffness (CAS) configurations. Secondly, the effect of wash-in and wash-out deformations on the flutter speed of both composite wing configurations. The wing models are generated using the finite element program FEMAP, v6 and analyzed using the standard FE software, MSC/NASTRAN, v70.5. Results from both model configurations are compared and discussed. It is shown that bending frequency is decreasing with increasing the fibre angle, where as the torsion frequency is a maximum at 0=±30° and ±45° for the CAS and CUS wing models respectively. It is found that bending-torsion coupling is more beneficial to the torsion frequency compared to the bending frequency. The positive coupling stiffness, which causes the wash-in behaviour, is found to increase the flutter speed of composite wings compared to the wash-out behaviour. Further more, coupling material stiffness is more beneficial to the flutter speed as in the case of CAS wing model compared to the CUS wing model.