This study investigates the processes and characteristics of solids removal in two types of permeable pavement: UNI Eco-Stone and porous asphalt. The mechanisms and processes behind solids removal within permeable pavement structures was studied for these two types of permeable pavements using both field installations and laboratory experiments. Results from the study showed that both pavement types are capable of excellent total suspended solids removal, in the range of 90 to 96% removal of solids from influent. Particle size distribution analysis of accumulated sediment within the pavement structure and in the influent and effluent showed that the particles in the effluent of the pavements are substantially finer than that in the influent. Laboratory results involving no crust formation indicated that, although solids removal occurs throughout the entire structure, the "sieving action" occurs primarily at the geotextile interface.