Individuals with elevated social anxiety appear particularly vulnerable to experiencing alcohol-related problems; yet we know little about factors that may account for this relationship. One possibility is that socially anxious individuals hold beliefs about the impressions they make on others while drinking and these beliefs play an important role in their drinking behaviors. The present study used exploratory factor analysis among participants with clinically elevated social anxiety (n=166) to develop a measure, the Social Impressions while Drinking Scale (SIDS), to assess beliefs regarding others' impressions of drinking behaviors that may be particularly relevant to socially anxious individuals. A valuations scale was also developed to assess the importance of each belief. Empirically-derived subscales were identified with adequate reliability. Among socially anxious participants, the Gregarious and Sexual Facilitation subscales were uniquely related to drinking problems and frequency respectively. Individuals with clinically meaningful social anxiety achieved higher scores on all SIDS subscales compared to those with lower social anxiety (n=166). Several SIDS scales mediated the relations between social anxiety group status and drinking problems (Interaction Fears, Observation Fears, Aggression, Gregariousness). Results highlight the importance of examining beliefs specific to high-risk populations in assessing their alcohol-related behaviors.