Periodically regenerable cake-forming filters are used to separate particles from gases having high dust concentrations, whereby the separation arises as the dust-gas mixture passes through the filter medium and the particles are retained. During the build-up of the filter cake, the pressure drop over the filter increases, making regeneration of the filter medium indispensable. The regeneration is performed at a defined maximum pressure drop across the filter and, after regeneration, the next filtration cycle starts and a new dust filter cake is built-up on the cleaned filter medium. The residual pressure drop is a measure of the dust remaining in the depth of the filter medium. Unfortunately, it quite often happens that the residual pressure drop does not reach a constant value after several filtration cycles, but increases steadily as a result of the fact that not all of the filter cake is removed by cleaning. This paper presents a mathematical model that is capable of simulating the time-dependent build-up of dust filter cakes, on the surface of filter, and includes calculations of the corresponding pressure drop and the thickness of the filter cake that formed during the filtration.