This study reviews 19 randomized controlled trials examining the association between three relationship factors - participation, treatment involvement, and therapeutic relationship - and outcome of cognitive-behavioral anxiety treatments for children and adolescents. In 12 studies, parent participation was considered as an independent variable compared to child-only participation. In three studies, parental involvement was measured. Child involvement was measured in one study. The child's perception of the therapeutic relationship was considered in three studies. Six studies found a significant positive effect of parent participation on diagnostic status, symptom level, or global functioning outcome measures. One study found a significant effect of parental involvement on global outcome measures. Another study found a significant positive association between child involvement and symptom measures and global functioning measures. No association was found between the quality of the child's perception of the therapeutic relationship and treatment outcome. Clinical implications are discussed.