Air pollution is the most important environmental risk factor for human health, affecting an average of 400,000 premature deaths in the EU and costing Europeans an average of more than € 166 billion a year. In the case of the cities of Ljubljana and Maribor, external costs amount to almost EUR 271 million annually. Estimation of external costs of air pollution from transport is slightly decreasing. The trend is influenced by the competitiveness of public transport, implementation of measures to limit personal traffic on fossil fuels, and the electrification of the vehicle fleet in cities.