A new multi-scale model of urban air pollution is presented. This model combines a regional chemical transport model (CTM) with spatial scales down to 1 km and a street-network model. The street-network model MUNICH is coupled to the Polair3D CTM to constitute the Street-in-Grid (SinG) model. SinG and MUNICH are used to simulate the concentrations of NO_x and ozone in a Paris suburb. SinG shows better performance than MUNICH for NO₂ measured at monitoring stations within a street canyon.