Although periods of heightened anxiety are part of normal psychological development (Gullone et al., 2 001; Stevenson-Hinde, & Shouldice, 1995; Westenberg et al., 2 004), a significant proportion of all children and adolescents report anxiety levels above developmentally appropriate levels and in some of these children and adolescents the anxiety levels may be so severe that they can be diagnosed as an anxiety disorder (Verhulst et al., 1997). In childhood and adolescence, anxiety disorders are among the most frequently assigned psychiatric diagnoses (Bernstein & Borchardt, 1991). Based on self reports (Diagnostic Interview Schedule for Children: DISC; Shaffer et al., 1993) the prevalence of anxiety disorders in Dutch adolescents (aged 13-18 years) is approximately 10.5 percent (Verhulst et al., 1997). These disorders may be chronic and substantially disrupt the quality of life and development of the children and adolescents involved (Bastiaansen et al., 2 006; Keller et al., 1992; Ollendick and King, 1994). The most frequently diagnosed anxiety disorders during childhood and adolescence are: Separation Anxiety Disorder, Generalized Anxiety Disorder, and Social Phobia. There may be a developmental trajectory underlying the origin of these anxiety disorders, as the average age of being diagnosed with a Separation Anxiety Disorder seems to be significantly lower than, for instance, Generalized Anxiety Disorder, a disorder becoming more prominent during adolescence (Westenberg et al., 1999, 2 001).