The assessment of client satisfaction has become an important aspect of evaluation research in the adult mental health field, but there has been relatively little extension of that approach to the child client population. This is due to the lack of adequate methodologies for assessing treatment satisfaction in children and to the overriding conceptual issues which make it difficult to develop such measures. Further information is needed to clarify developmental differences in the way both healthy as well as medically and psychiatrically ill children conceptualize illness and treatment. The authors suggest that specific methodologies for assessing child satisfaction with treatment can be systematically developed once a more explicit developmental framework has been delineated in the area of children's understanding of medical and psychiatric disorders and their treatments.