The present paper is devoted to the mechanism of vortex enhancement and the occurrence of lip vortices in contraction flows of viscoelastic fluids. The FENE-P model was used in order to simulate earlier experimental results of Evans and Waiters for the flow of aqueous polyacrylamide solutions through planar contractions. The influence of the contraction ratio, the polyacrylamide concentration and the corner sharpness were investigated. In all cases, numerical simulation gave qualitative agreement with experiments.