Transport of colloidal particles is governed by the rate at which the colloids strike and stick to collector surfaces. Filtration theory has classically neglected the influence of hydrodynamic forces and pore structure in the calculation of collision efficiency, as well as non-idealities associated with natural porous media such as non-spherical collectors and rough surfaces. Computational simulations will be presented that consider the influence of hydrodynamic and DLVO forces on colloid attachment to variously shaped collectors, and colloid retention processes that occur in small pore spaces formed by multiple collectors and rough surfaces. Our analysis indicates that hydrodynamic forces, collector shape, and pore structure significantly influences the colloid collision efficiency. Colloid attachment is only possible in regions of the pore space where the torque from hydrodynamic shear that acts on colloids adjacent to collector surfaces is less than the adhesive (DLVO) torque that resists detachment. The fraction of the collector surface area on which attachment may occur increased with solution ionic strength and decreasing flow velocity. Our results also show that the collision efficiency is sensitive to collector features such as roughness and shape, and to the pore space geometry. Simulation findings demonstrate that quantitative evaluation of colloid transport through porous media will require nontraditional approaches accounting for physical (hydrodynamics, surface roughness, collector shape, and pore structure) and chemical (DLVO forces) conditions.