This paper deals with a post-process to obtain a more accurate approximation of the fluid pressure from a finite element computation of the vibration modes of a fluid-structure coupled system. The underlying finite element method, based on a displacement formulation for both media, consists of using Raviart-Thomas elements for the fluid combined with standard continuous elements for the solid.An easy to compute post-process of the pressure is derived. The relation between this post-process and an alternative finite element approximation of the problem based on discretizing the fluid pressure by enriched CrouzeixRaviart elements is studied. Higher order estimates for the L 2 norm of the post-processed pressure are proved by exploiting this relation. As a by-product, higher order L 2 estimates for the solid displacements obtained with the original method are also proved. Member of CIC, Provincia de Buenos Aires, Argentina Member of CONICET, Argentina. Partially supported by FONDECYT 7.990.075 and FONDAP in Applied Mathematics, Chile Partially supported by FONDECYT 1.990.346 and FONDAP in Applied Mathematics, Chile 390 A. Alonso et al.