This project explores how experienced adult users of social media disclose personal information over online social networks (OSN). This work introduces a four-dimensional model to serve as a foundational framework for the study of online self-disclosure (OSD); these four dimensions are personal, social, technological and contextual, and support the complexity of decision-making behind OSD. The dissertation is comprised of two complementary studies that explore OSD in quantitative (survey, n=1092) and qualitative (interviews, n=21) terms. Results reveal how variables related to the four dimensions of the model can have strong influence in OSD processes and how these variables and dimensions are interconnected. Findings reveal that there are differences in perceptions of intimacy for particular channels and that this influences OSD behaviors, also that the intended audience plays a central role in OSD decisions, and that the intended audience is critical for channel selection. The first study provides robust data on some important factors that influence OSD, including frequency of use as a strong predictor of OSD: the second study gives a nuanced picture of how experienced users share personal information on OSN. These interviews reveal a strong role of OSN in relationship maintenance and development; they also speak of a positive role of OSD in people's lives. In general, we find support for the four dimensional model, suggesting that future research on OSD gains in robustness from exploring factors from all of these dimensions. This research also makes methodological contributions; the methods used here have been shown to be effective and can be re-purposed and enhanced to explore this phenomenon further, and to test these results on different populations. The results in general speak of highly adept people making complex decisions on the fly, as well as positive yields from online disclosure. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]