Currently, there is considerable variability and ambiguity in legal standards pertaining to juveniles' comprehension of Miranda rights and their adjudicative competence. This study investigated rates of impairment under various proposed legal standards. One hundred and fifty-two young defendants aged 11–17 were assessed with Grisso's Miranda Instruments and the Fitness Interview Test—Revised. While over half of defendants aged 15 and under were classified as impaired in adjudicative capacities when adult norms were applied, significantly fewer adolescents were classified as impaired when adolescent norms were applied or a standard of “basic understanding and communication.” Also, while over half of defendants aged 15 and under were classified as impaired in their comprehension of Miranda rights when both understanding and appreciation of Miranda rights were required, significantly fewer youth were classified as being impaired when only understanding was required. The implications of these findings are discussed. Copyright © 2007 John Wiley & Sons, Ltd.