Product-Service Systems (PSS) design is far from reaching maturity when dealing with early concept generation and selection tasks. Several methods and models for Multi-Criteria Decision Making (MCDM) are proposed in the literature to augment the ability of the design team to identify, early on in the process, the most valuable solution option(s). The aim of this chapter is to review how MCDM is applied today to guide design concept selection activities in the PSS realm. It lists and discusses the most popular techniques used by the research community to deal with the choice, ranking and sorting problems for design decision-making, pointing to application cases across several industrial sectors. Building from the results of a multiple case study analysis, it further proposes 5 ‘questions to be asked’, reflecting on the selection and usage of the MCDM techniques when approaching PSS design vs. classical product development and systems engineering