Moisture diffuses through the pore space and the fiber matrix in paper materials. The diffusivity through paper increases strongly with moisture content. We measured the moisture diffusivity of handsheets made of refined bleached kraft pulp at various relative humidity conditions. Steady state moisture fluxes were measured and diffusivities in the lateral (x-y) and in the transverse (z) directions were calculated.The lateral diffusivity was found to be higher than the transverse diffusivity for all the samples and the effective moisture diffusivities depended strongly on the moisture content.