The main explanatory hypothesis for the distinction between social phobia (SP) and avoidant personality disorder (APD) has been the severity continuum hypothesis, stating that APD only differs from SP in terms of severity of dysfunction and symptomatic distress, that is, social anxiety and depressive symptoms. This study aimed at a comprehensive evaluation of this hypothesis in a large sample (n = 2192) of thoroughly assessed patients, most of whom had a diagnosis of personality disorder. Social phobia was stronger associated with APD than with other personality disorders, and APD was stronger associated with SP than with other symptom disorders. Social phobia-pure patients had a higher level of global functioning and lower levels of general symptom distress and interpersonal problems than APD-pure patients. The 2 groups were similar on domains that pertain to social anxiety and introversion, but APD was associated with a broader array of symptoms and interpersonal problems and was substantially lower on the personality domain of conscientiousness. Avoidant personality disorder was stronger associated with eating disorders, and SP was stronger associated with panic disorder. The APD diagnosis seems to capture a broader constellation of symptoms and personality features pointing toward more severe personality dysfunction. Our findings suggest that the severity continuum hypothesis lacks specificity and exploratory power to account for both similarities and differences between SP and APD.