We present results for gas absorption into a liquid film flowing over a spinning disc. The flow is accompanied by the formation of nonlinear waves which strongly influence the diffusion boundary-layer that develops beneath the surface of the film. We use recent advances in modelling of the hydrodynamics and solve a two-dimensional convective-diffusion equation for the solute concentration. Numerical solutions for the finite-amplitude wave regimes and associated integral absorption rates are obtained for flow conditions corresponding to real experiments. Our results show clearly the enhancement of absorption due to the waves. (c) 2005 Elsevier Ltd. All rights reserved.