Necessity of adaptation the Polish law in the field of the environment protection to the European Union law caused to adopt new criterions and methods of the air quality assessment. One of the methods of the air quality assessment is modeling of the substance levels in the air based on the calculation of the air pollutant dispersion in the atmosphere. Thus necessary changes also encompassed the basic methodology applied in our country for many years that had made possible calculation of the air pollution caused by existing and new emission sources. After some modifications the computation method was adopted as the reference modeling methodology. In the paper scale of the changes and their influence on the intermediate and final computation results were presented.

English title: Comparison of the previous and the current methodology of modeling the pollutant dispersion in the air based on the Gaussian plume model.