The limited spatial area in conventional diesel particulate filter (DPF) systems requires frequent regenerations to remove collected particulate matter (PM) emissions, consequently resulting in higher energy consumption and potential material failure. Due to the complex geometry and difficulty in access to the internal structure of diesel particulate filters, in addition, many important characteristics in filtration processes remain unknown. In this work, therefore, the geometry of DPF membrane channels was modified basically to increase the filtration areas, and their filtration characteristics were evaluated in terms of pressure drop across the DPF membranes, effects of soot loading on pressure drop, and qualitative soot mass distribution in the membrane channels. In this evaluation, an analytical model was developed for pressure drop, which allowed a parametric study with those modified membranes. This parametric study was conducted in a bench-scaled DPF test system with pressurized air, which revealed the detailed characteristics of filtration processes in the modified DPF membranes and provided optimum design criteria for improving filtration and regeneration efficiencies. The soot cake formation in the expanded filtration areas was visualized by a unique micro-imaging system, suggesting further detailed examinations.