Evaluation and long-term assurance of customer satisfaction are integral elements of quality management in libraries. Quality defined as " all features and functions of a product or service that influence the way that product or service meets certain specified demands" (EOQ , 1976) is subjective in the case of each individual customer but the opinions of those customers make the basis for general evaluation which may help library in analyzing its strengths and weaknesses. The author discusses various initiatives taken by Forschungszentrum Jülich Central Library in order to retain its customers and presents results of online research performed in 2007 by the library in order to enhance the quality of its products and services.