This special issue of the Scandinavian Journal of Public Health is devoted to articles on the Copenhagen Psychosocial Questionnaire (COPSOQ). I have been asked to participate with a personal contribution and have been given the freedom to write whatever I find appropriate. My main message in this article is that a questionnaire is not just a questionnaire. A questionnaire, such as COPSOQ, is a tool for creating theoretical insight, an eye opener for employees and employers, a way to create a new language, a bridge for building long lasting ties between researchers and workplaces, a way to give legitimacy to the field of psychosocial factors at work, an instrument for creating new personal and professional friendships, and – last but not least – a tool for improvement of the working conditions for thousands of employees and for increasing the productivity of the companies. I cannot cover all these aspects in detail but I will touch upon most of them in the following.