To investigate the effect of single windbreak and combination of hill and windbreak on pollutant dispersion in neutral boundary condition, CFD (Computational Fluid Dynamics) modeling was used. The validity of the CFD model was confirmed by wind tunnel and field experiments of single closed windbreak. The results show increased windbreak height increasing the height of maximum concentration position and decreasing surface concentration (x=50 m) from 1.5 to 5.0 times smaller than that of non-windbreak case. In combination of hill and windbreak case increasing hill height decreasing surface concentration from 1.0 to 1.1 times smaller than that of single windbreak case.