This study explores whether participation in the US Federal Emergency Management Agency's Community Rating System (CRS), a voluntary community flood risk management program, is a function of policy diffusion or an act of free-riding. Policy diffusion would suggest that, all else being equal, once a community has joined the CRS, neighboring communities will be more likely to follow their lead and participate in the CRS. Free-riding would imply that neighboring communities might choose not to participate in the CRS because they perceive that their community benefits from surrounding communities' participation. Results indicate that a community's decision to participate in the CRS is not influenced by the characteristics of or the behavior of their neighbors. The results of this study do, however, show that population density, aggregate housing values, rentership rate, and flat topography are significant predictors of CRS participation.