Although HDR content processing, coding and quality assessment have been largely addressed in the last few years, little to no work has been concentrating on how to assess quality in HDR for 360 or omnidirectional content. This paper is an attempt to answer to various questions in this direction. As a minimum, a new data set for 360 HDR content is proposed and a new methodology is designed to assess subjective quality of HDR 360 content when it is displayed on SDR HMD after applying various tone mapping operators. The results are then analyzed and conclusions are drawn.