Given the high rates of co-occurring marijuana use and social anxiety, the present investigation examined the relations among marijuana use motives, marijuana use and problems, and social anxiety in 159 (54.7% female) young adults (M(age)=18.74, SD=1.20). As expected, after covarying for a number of variables related to both marijuana use and social anxiety (e.g. gender, alcohol use problems, anxiety sensitivity), social anxiety predicted greater numbers of marijuana use problems. Interestingly, social anxiety was not related to marijuana use frequency. Also consistent with prediction, social anxiety was a significant predictor of coping and conformity motives for marijuana use above and beyond relevant variables. Finally, coping motives for marijuana use mediated the relation between social anxiety and marijuana use problems. These data provide novel evidence for the unique effects of coping-motivated marijuana use in the link between marijuana-related impairment and social anxiety.