Although it is clear that people with social phobia have interpersonal impairment, evidence that social phobia (as opposed to other mental disorders) affects friendship in particular is lacking. Two large epidemiological datasets were used to test whether diagnosis of social phobia is related to perceived friendship quality above and beyond perceived family relationship quality, diagnosis of other mental disorders, and a variety of demographic variables. After Bonferroni correction, social phobia was the only diagnosis related to perceived friendship quality above and beyond other factors, such that people with social phobia reported more impaired friendship quality. Social phobia's effect was similar in magnitude to demographic characteristics in both samples. The current study demonstrates that social phobia is specifically related to perceived friendship quality, suggesting that this aspect of social phobia's effects is worthy of further study.