Social Anxiety Disorder (SAD) is a heterogeneous and distressing problem for many children and youth. This review focuses on the etiology and maintenance of SAD, and examines research findings in several key areas of investigation: genetic or hereditary factors (twin and family studies), temperament characteristics (behavioural inhibition), and parent–child interactions (attachment, parenting styles). It is concluded that genetic influences, behavioural inhibition, and parent–child interactions play significant and interactive roles in the development and maintenance of SAD. Other influences such as peer relationships, social skills deficits, and traumatic experiences are also acknowledged. Ultimately, an understanding of such pathways should facilitate effective early screening and intervention of children at risk for severe social anxiety.