The study aims to identify the information useful to support a patients' EDs' choice in order to design a patient Web-based system. For that purpose, a focus group and a formative user test have been performed. The results show that five types of information can be relevant. The spontaneous favored information is the "distance" to EDs. The "Wait time", that is sanctified in literature, is only used in a second time. A larger summative evaluation should be planned to evaluate and validate the befits of this kind of tool.