Prior work indicates the presence of a subtype of Social Anxiety (SA) characterized by disinhibition or high externalizing behaviors such as substance use and Attention Deficit Hyperactivity Disorder (ADHD) symptoms. A sample of 375 undergraduates completed an online study including measures of SA, substance use, ADHD symptoms and impulsivity. Latent class analyses revealed three classes of individuals who evidenced: (a) low SA and low impulsivity, (b) high SA and low impulsivity, and (c) high SA and high impulsivity. Individuals high in both SA and impulsivity evidenced greater likelihoods of exhibiting externalizing behavior, relative to the two other classes. Post-hoc analyses revealed the largest and most significant differences between classes were seen with regard to ADHD. This finding extends previous work by replicating distinct profiles of SA and impulsivity, and highlighting that how these profiles relate to externalizing behaviors may depend on the externalizing domain.