Despite continued research into the Community of Inquiry (CoI) framework, the best way to measure each presence of the framework, and in particular social presence, has not been effectively settled in prior research. The purpose of this study was to evaluate the validity of the social presence items in the CoI framework and its subscales, as well as to determine the strongest contributors to the social presence construct. An online survey of 413 students in online courses in the U.S. was administered to assess the validity and structural framework of the social presence construct. The findings from the current survey suggest that social presence is most strongly predicted by affective expression, and that all three subscales explain approximately 72% of the variance in social presence. The implications of this variance and future research items suggest that emotional expression is one of the more important factors for instructors to focus on in online courses to promote social presence.