To estimate the residence times of aerosols in air, the activities of $^{210}Pb$ and $^{210}Po$ in aerosols were measured at 4 sites in Pusan. All aerosol samples were collected by a high volume air sampler from January to October 1996. The activities $^{210}Pb$ and $^{210}Po$ in Pusan were varied from 11.77 to 67.57 dpm/1000$m^3$ and from 2.63 to 15.91 dpm/1000$m^3$, respectively. The mean activities were 34.62 dpm/1000$m^3$ for $^{210}Pb$ and 8.24 dpm/1000$m^3$ for $^{210}Po$. The highest values of the activities of $^{210}Pb$ and $^{210}Po$ were appeared at P3 site and the lowest values at P4 site. During the sampling period, the trends of the activities of $^{210}Po$ and $^{210}Pb$ were similar to total suspended particulate matter(TSP) concentrations. The mean residence times of atmospheric aerosols calculated from $^{210}Po$/$^{210}Pb$ activity ratio was about 60~80 days in Pusan. The longest residence time of atmospheric aerosols was in January because of the lack of rainout and washout, but the shortest residence time was in August, largely due to scavenging effect by frequent rains. The activities of $^{210}Po$ and $^{210}Pb$ in atmospheric aerosols were different in time and space, which seems that the distribution of $^{210}Po$ and $^{210}Pb$ activities and scavenging processes in air may be controlled by the local and meteorological conditions.