Information and Communication Technologies (ICT), and particularly Social Media, drastically changed communication channels and organization during a crisis response. In this context, new forms of citizen initiatives appear, contributing to situational awareness, providing new profiles of stakeholders and broadening the scope of volunteerism in disaster situations. Thus, given the increasing need to understand and take citizen initiatives into account, this article provides a taxonomy of volunteerism types in crisis contexts, based on a literature review on the subject. Mapped on two main dimensions: the status (who they are) and the focus (what they are doing), multiple types of volunteers are presented on this taxonomy. Then, the article deals with possible use of this taxonomy towards integration of citizen initiatives into the crisis response.