This paper is focused towards dimensional analysis in ESP model building, showing both the reduction in effort and more effective modeling that can result. Electrostatic precipitators (ESP) are widely used in industry today and much research has been carried out during the last decades. However, dimensional analysis is still an unsettled matter, in spite of it allows to reduce the number of parameters necessary for defining the ESP performance, provides a reliable scaling-up of the desired operating conditions from the pilot-scale to full-scale plant (based on the invariance of the pi-space) as well as a consistent extrapolation within the range covered by dimensionless numbers, and gives a greater flexibility in choice of parameters. This analysis together with the similarity analysis is presented in this work, in order to obtain a functional dependence between a target number and a set of few dimensionless numbers. The target selected has been the ratio of particle dust concentration at the outlet of the ESP and that at the inlet of the ESP. Thus, after doing these analyses, several quite reduced models have been formulated theoretically and later tested and validated with experimental data obtained in a pilot ESP, in order to show an application of the study. By this way, a non-linear regression model matches well with experimental data from a pilot plant. (C) 2011 Elsevier Ltd. All rights reserved.