The present article focuses on data collection through web questionnaires, as opposed to the traditional pen-and-paper method for research in second language acquisition and bilingualism. It is argued that web questionnaires, which have been used quite widely in psychology, have the advantage of reaching out to a larger and more diverse pool of potential participants, which may increase the ecological validity of the resulting database. After considering some issues raised in debates on the strengths and weaknesses of traditional approaches to data collection through questionnaires as opposed to web-based questionnaires, we present two case studies of research designs based on online questionnaires, that is, the bilingualism and emotions questionnaire (Dewaele and Pavlenko, 2001/03) and the feelings questionnaire (Wilson, 2008). We reflect on the issue of participant self-selection and conclude that the potential benefits of web-based questionnaires can outweigh their limitations.