The paper discusses research results regarding the influence area of cultural institutions located in Łódź. The analysis includes data collected from nine biggest museums and theatres. In order to gather the information, customers were asked for their zip-codes. This method allows for surveying a large group of people and at the same time it does not interfere much with current activity of the institution. During the spring of 2012, the information about places of residence of 35 thousand customers who visited cultural institutions in Łódź was gathered.