Social Anxiety Disorder (SAD) and Autism Spectrum Disorders (ASD) are fairly common psychiatric conditions that impair the functioning of otherwise healthy young adults. Given that the two conditions frequently co-occur, measurement of the characteristics unique to each condition is critical. This study evaluated the structure and construct overlap of two screening measures of SAD and ASD. Results from 623 young adults indicated that separable, though highly correlated, factors can be derived from the two measures related to social anxiety and social difficulties. The ASD screening measure also taps unique factors related to restricted interests and attention to details, theory of mind deficits, and a preference for routine. Recommendations are provided for accurate screening of symptoms of both SAD and ASD.