Transient diffusion and adsorption processes of one component in a bidisperse pore system are studied. The solid network is described by the branched micropore-macropore model. A criterion to identify the controlling mechanism, macropore diffusion, micropore diffusion, or both, is suggested. This criterion based on diffusional information and pellet geometry is compared with the criterion for bidisperse systems with homogeneous diffusion at the microscale level. The effects of the nature of the adsorption isotherm (linear, Langmuir, and irreversible) in concentration profiles and in uptake are analyzed. The mathematical model is analytically solved for linear systems, and solutions for the macropore or micropore diffusion control cases are also obtained. Numerical solutions of concentration in macro- and micropores for the three isotherms are obtained using orthogonal. collocation in finite elements. For irreversible systems an analytical expression for uptake is derived on the basis of a simplified model. The time dependence of the uptake for the three possible mechanisms is also addressed.