Background: Advance care planning (ACP) enables persons to identify preferences for future treatment and care, and to discuss, record and review these preferences. However, the uptake of ACP among patients with chronic diseases is relatively low. Web-based ACP programs can support patients and their relatives in ACP. However, information needs of patients and their relatives for ACP are unknown. The aim of this study is to explore information needs of patients with chronic disease and their relatives for web-based ACP.