A theoretical model describing the unsteady-state transport of moisture in the thickness direction of paper is formulated that accounts for the parallel diffusion of moisture in the pore and fiber phases, as well as external mass-transfer resistance. Using values of the effective water-vapor and bound-water diffusion coefficients of a bleached kraft paperboard (BKP), which were estimated from steady-state moisture flux measurements in the first part of our work (see the preceding article in this issue), and no fitting parameter, the predictions of the dynamic moisture-transport model are found to be in good agreement with measurements of the transient weight change and relative humidity (RH) profile of stacks of BKP sheets subjected to ramp changes of the external RH under a variety of experimental conditions.