An analytic solution for polydispersed aerosol dynamics by wet deposition of droplets was obtained, The collection efficiency used was based on the results of Jung and Lee (Aerosol Sci. Technol. 29 (1998) 389). The derived efficiency was compared with the existing formula of Slinn (Atmospheric Science and Power Production- 1979, Division of Biomedical Environmental Research, U.S. Department of Energy, Washington DC, USA, 1983 (Chapter 11)) and showed good agreement. The particle size distribution was assumed to have a log-normal function, and the Cunningham slip correction factor was simiplified to introduce the moment relationship. Both analytic and numerical solutions were obtained and compared with each other. The results show that the analytic solution can simulate the scavenging of polydispersed aerosol by wet deposition for the diffusion-dominant range well. The particle diameter of minimum collection efficiency was obtained analytically. It was found that the minimum collection efficiency diameter increases with decreasing velocity and decreasing packing density. (C) 2002 Elsevier Science Ltd. All rights reserved.