Digital Twins (DTs) are among the most hyped technologies of the 2020 s. Yet, the research dealing with the use of DTs in early Product-Service Systems design remains insufficiently systematized. Based on the findings of multiple-case studies in the Swedish manufacturing industry, the objective of this paper is to collect and present a set of ‘questions that need to be answered’ to foster the development and utilization of DTs in the PSS realm. The results highlight how the DTs should be composed of several layers to boost value co-creation in design, in a way to incorporate the digital ‘counterpart’ for more abstract entities, from processes to human behaviors to more intangible assets.