An experimental study has been carried out to determine the aerosol charge distribution through photocharging process: Particle charge distribution was studied in dependency on particle number concentration and irradiation intensity. While highly positively charged aerosol's were obtained for particle number concentrations below 5 x 10(11) m(-3), approximately symmetrical bipolar charge distributions were measured for number.,concentrations of about 2 x 10(13) m(-3). The theoretical description was made on basis of the previously developed model, which was extended by a term accounting for ion diffusion losses. Theoretical results reflected experimental Observations. The necessity of taking into account diffusion discharging of particles by gas ions is'det6rmined by a dimiensionless factor depending on initial parameters. Since the charge distribution through photocharging becomes a known function of particle and irradiation parameters, a photocharger may be used instead of a neutralizer to produce a defined charge distribution. (C) 2002 Elsevier Science Ltd. All rights reserved.