Social Anxiety Disorder is a heterogeneous and distressing problem for many children and youth. Unravelling its multiple causes is essential for a full understanding of the condition. This selective 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). We conclude that genetic influences, behavioural inhibition and parent-child interactions play significant and interactive roles in the development and maintenance of social anxiety disorder. Other influences are also acknowledged, such as peer relationships, social skills deficits and traumatic experience. Ultimately, an understanding of such pathways should facilitate effective early screening and intervention of children at risk for severe social anxiety.