Implementing an Electronic Health Record (EHR) is a sociotechnical process. End-users' expectations and attitudes need to be monitored during the implementation of a new EHR. It is not clear what end-users consider the most important determinants (both barriers and enablers for a successful EHR implementation) during this process. Based on the concept mapping method and a literature search we developed a questionnaire to investigate which determinants (future) end-users of an EHR consider important. Additionally we analysed whether there are differences between a centre working with a legacy EHR and one with paper-based patient records before implementation. We identified the following determinants: usability of EHR, availability of facilities, alignment with work processes, support during implementation, training on new EHR, support after implementation, practice with new EHR, internal communication, learning from other centres, reuse of patient data, general IT skills, and patient involvement in decision making. All determinants were perceived important by end-users to successfully work with an EHR directly after its go-live. The only two significant differences between centres were knowledge about the effect of the EHR on work processes, and importance of patient involvement in decision making.