The aim of this article is to assess the impact of the tax in the special economic zones on the state of finances of territorial council. The investigation was based on the example of first Polish special economic zone the SSE Euro-Park Mielec. The period of functioning of the zone in Mielec was described from the point of its establishment in 1995. The analysis which was carried out showed that it is not essential for the local budget if the zone inventors have the tax exemption. What is more, it was noticed that there was a notable growth of budget's income from the income taxes and real estate taxes. It was the result of the dynamic development in enterprise in the region of collapsing industry. The inflowing investors to the zone of Mielec, who were encouraged by the given tax privileges, contributed the formation of next companies in the area. The SSE Euro-Park Mielec ended the monoculture of the industry through the diversification of the structure of industry. However its most important contribution was overcoming the crisis on the labour market - unemployment rate is nowadays less than the average for Poland and Podkarpackie province. The example of Mielec confirms the high effectiveness of the special economic zones as the stimulating instrument of economic development, particularly on the regional level. Preferential tax policy had consequences in the economic promotion of regions in Poland, not only in the country, but abroad as well.