Preservation of digital information is a vexing problem for preservation agencies. Properties or functionalities of the preserved object can be lost over time. Digital preservation is an ongoing, proactive process of preserving information and its significance over time. In this article, we conduct a theoretical and an empirical study in Swedish preservation agencies to identify and define a set of essential information properties for long-term preservation. Among identified properties, the study confirmed that knowledge on how to guarantee quality of preserved digital information is low and showed that guiding quality principles need to be established. The need for a unified information quality assurance framework was also highly confirmed.