We used the 2008 West Bohemia (WB) swarm earthquakes to characterize the seismic attenuation in the region. We found effective attenuation factors ranging between 150 and 175 and between 125 and 165 for most of the stations. We developed an innovative differential attenuation measurement method that shows significantly lower values in the source region of and , consistent with a saturated and fractured rock mass in the source region. Furthermore, stations placed west of the main fault system show a statistically significant temporal decrease in the effective attenuation coefficient. The effective attenuation coefficient is the lowest for the SKC station, the closest station to the mofettes with a high flow of . The observations of the temporal changes are consistent with flow and fluids.