With the recent expansion of child mental health research, more attention is being paid to the process of informed consent for research participation. For the consent to be truly informed, it is necessary that the relevant information be both disclosed and actually understood. Traditionally, much effort has gone to ensuring the comprehensiveness of consent/assent documents, which have progressively increased in length and complexity, whereas less attention has been paid to the comprehensibility of these documents. Available data indicate that many parent and children have difficulties appreciating the research nature of treatment studies and that a higher level of formal education among the parents is associated with a greater degree of understanding. Promising approaches to achieving truly informed research participation have emerged, such as additional time for parents to meet with the researchers and using postexplanation questionnaires for identifying issues in need of further clarification. Research is needed to develop and test strategies for improving the effectiveness of the informed consent process in child mental health.