Citizen science is a form of research collaboration that involves the public in scientific research to address real-world problems. Virtual citizen science projects, entirely mediated by information and communication technologies (ICTs), are often considered a form of crowdsourcing applied to science. The use of ICTs to support citizen science has already yielded significant impacts on the scale and scope of participation and research, but there is little guidance to help projects choose and implement appropriate technologies to support research and participation goals. This dissertation study employs a comparative case study methodology to examine how virtuality and technology shape processes of organizing and participation in citizen science, and how these processes influence scientific outcomes. The goal of the study is to conceptualize virtual participation by examining the relationship between ICT and practice in order to inform design and management of cyberinfrastructure for citizen science.