Global sea‐level changes have been occurring since the last Pleistocene deglaciation. Recently the contribution of current postglacial rebound to local sea‐level variations has been removed by means of a radially stratified earth model in order to assess the amount of sea‐level rise due to recent climatic changes. We have studied the effects of lateral variations in the viscosity structure on the postglacial uplift rates along the continental margins. Finite‐element calculations in cylindrical geometry show that the spread in the cumulative vertical displacement may be affected by 20% in the presence of lateral rheological contrasts. But the vertical rates of deformation can attain differences of up to 50% for the different models. Horizontal deformation rates along continental margins are much more affected by the lateral variations in viscosity and can be used in the future as constraints on mantle rheology.