The model calculations of oil-shale fly ash deposition from the Narvapower plants (north-eastern Estonia) are performed using the models HILATAR (regional scale) and AEROPOL (local scale). The modelling results are compared with air quality monitoring results from the observation stations in the Baltic Sea region and with the results of snow pollution study in Estonia. It was found, that although the bulk of the ash emitted is deposited near the sources, the emissions are large enough to create remarkable background deposition in the Baltic Sea region. The uncertainties related to the effective particle size are discussed and corresponding sensitivity studies are performed.