Checklists can be used to improve and standardize safety critical processes and their communication. The introduction of potentially harmful medical technology and equipment has created additional requirements for the safe delivery of health care. We have studied the implementation of an electronic checklist to ensure the safety of patients scheduled for Magnetic Resonance Imaging examinations. Through a combination of observations and semi-structured interviews we investigated how health care workers in a Norwegian University hospital dealt with variations in checklist compliance, missing and lack of information. The checklist provided different functionality for the different users, ranging from a memory/attention support to a standardized form of communication on safety matters. However, the rigidity afforded by the electronic implementation, showed some serious drawbacks over the prior, simpler, paper-based versions.