In this paper, results of Eulerian grid and Lagrangian photochemical model simulations of emmissions from a major elevated point source are presented. A series of simulations with grid sizes varying from 30 km to 2km were performed with the Urban Airshed Model, a photochemical grid model, in order to examine the capability of the model to resolve plume features and to emulate the chemical evolution of the pollutant plume. Differences in pollutant concentrations with emphasis on O3 for various grid sizes are highlighted. The grid model simulation results are compared to O3 concentrations generated from a Lagrangian reactive plume model (RPM). Both models were applied to treat the transport, dispersion, and photochemical processes impacting a pollutant plume. In order to promote the comparison and interpretation of the model results, meteorological inputs for the Lagrangian plume model were provided through an interface program using the input data sets employed to drive the grid model.