Although user participation may facilitate the realisation of IT innovations, various literature analyses show only minimal to moderate evidence for such effects possibly due to disregard of mediating factors. Against this background, this study examines the extent to which joint intrapreneurship of clinical leaders and IT leaders as well as a distinct innovation culture mediate the effect of user participation on hospitals' IT innovativeness. IT innovativeness was measured by the availability and usability of IT functions and by the perceived 'innovative power' of a hospital. An empirical model was developed and tested with data from 168 clinical leaders and IT leaders who participated pairwise in a survey representing 84 German hospitals. Three parallel mediation analyses indicated that the participation of users could only lead to IT innovativeness if they were accompanied by intrapreneurial leadership on the part of clinical directors and IT leaders and if a pronounced innovation culture prevailed.