Abstract Water barrier properties of three treated papers and of one plastic film were compared and the potential of these packaging films to prevent moisture loss from a sponge cake during storage in standard conditions (25 °C and 50% relative humidity gradient) was evaluated. Sorption isotherms were established at 25 °C for both sponge cake and papers, from which diffusivity values in papers were determined for the whole range of A w. Permeability of packaging films was determined in standard conditions. Water sorption was close for all papers, regardless of their treatment, whereas water diffusivity was reduced by coating or calendering. Water vapor permeability in papers was controlled by diffusivity which was characterized by a two-phases (vapor then bulk water state) mechanism. Calendered-coated papers and plastic film were both adapted to prevent moisture loss from intermediate moisture foods such as a sponge cake during usual storage time.