Using a spatial hedonic price model, this study estimated the elasticity and the implicit marginal costs of variables related to air pollutants that may affect apartment prices in Seoul. Spatial econometric and interpolation methods were employed to estimate the benefits of changes in the concentrations of air pollutants. Previous studies showed that dependence, spatial heterogeneity, and air pollution concentrations can be addressed with the use of these methods. The average marginal willingness to pay with a 10% improvement in PM10 concentration is approximately 233,800 won (US$187.0) to 303,800 won (US$243.0) per month. With a healthy concentration (18.15% reduction), the average marginal willingness to pay is approximately 424,300 won (US$339.4) to 551,400 won (US$441.1) per month. Therefore, environmental factors can be important determinants of housing prices in Seoul. JEL Classification: R00, R15, Q53