Dust cake formation and structures on filters under the challenge of bimodal aerosol have been studied theoretically and experimentally. A theoretical model has first been derived based on bimodal aerosol loading with known particle mean sizes and geometrical standard deviations. The dust cake structure (average packing density or porosity) is expressed as a function of the operating conditions (pressure drop and filtration flow rate), the number ratio of two component bimodal particles, the particle characteristics of the respective component (e.g. particle size distribution and particle shape), and the total cake layer thickness. An experiment was then performed to verify the theoretical model. In the experiment, the dust cake height and pressure drop were measured in real time, and the loaded mass was inferred from the total collection time and the final mass measurement. The bimodal aerosol was generated by mixing both the alumina particles (0.7 μm mean diameter) and the Arizona Road Dust (2.0 μm) in the aerosol phase. Both types of particles were dispersed using a TSI Fluidized Bed Aerosol Generator. The experimental data correlate well with the theoretical model.