The article shows that business sentiment measured with general economic and sector barometers in Lublin province in 2004 was influenced by Poland’s accession to the European Union. In the second quarter of 2004, mood in the corporate sector was much better than suggested by forecasts taking into account long-term trends. A similar trend, though less intense, was noted in the third quarter. However, that optimism was short-lived. In the fourth quarter, business sentiment barometers were lower than predicted. This trend should be taken into account when analyzing business sentiment in the future.