There is an increasing expectation from the general public for information on abnormal situations occurring at a nuclear or a radiation facility. Historically communication of this information was restricted to highly technical experts. This report, established by communicators of Nuclear Regulatory Organisations is specifically dedicated to "communication in abnormal situations", that are defined as unexpected events or any situation likely to raise media and public concerns ("on the spot communication"). This report, resulting from exchange of experience between the WGPC members, highlights the main challenges to be addressed for communication in abnormal situation, other than emergency, indicates some prerequisite for an efficient strategy and the various means implemented in member countries to reach this objective.