The moisture diffusion during freezing of porous medium has been widely studied for low porosity matrix (i.e. concrete, rocks,...), whereas very few works are available for materials with high porosity. This work focuses on the evaluation of moisture diffusion of a model food (sponge) with a high porosity (in the range of porosity 0.90-0.94). The drying data has been obtained at positive temperatures (10-30 degreesC) for selected water content (25-142 g H2O/100 g DM). Then, the effective diffusivities have been estimated by using two different methods. Finally, moisture diffusivity in the sub-zero domain has been extrapolated by using an Arrhenius's model. During drying, the diffusivity increases as the average moisture content decreases. The temperature plays a significant role on the diffusivity. One of the two methods gives better results for the estimation of the effective diffusivity. (C) 2003 Elsevier Ltd. All rights reserved.