The purpose of this paper is to discuss and to compare existing approaches with the experimental data on the mobility of nm- and sub-nm-sized particles, and to propose a new model. Our model is based on the phenomenological consideration of collisions between a particle and gas molecules in the rough sphere approximation taking into account the energy exchange between translational and rotational degrees of freedom, ion-dipole interactions and sticking condition between these objects in the approach of random tangential forces. It was shown that the obtained expression for the electrical mobility of charged particles depends on the nature of the carrier gas. A comparison of different theoretical models with the experimental data (from 0.54 to 10.68 nm) showed the best agreement for our proposed model. It was shown that the ion-dipole interaction becomes significant for singly charged particles smaller than 1.2 nm and for doubly charged particles smaller than 2 nm. (C) 2005 Elsevier Ltd. All rights reserved.