To explore critical issues in the conceptualization and assessment of adolescent psychopathy, we report on the use of the Youth Version of the Hare Psychopathy Checklist-Revised (PCL:YV; Forth, Kosson, & Hare, 2003) and the Comprehensive Assessment of Psychopathic Personality-Institutional Rating Scale (CAPP-IRS; Cooke, Hart, Logan, & Michie, 2004)—both derived from procedures for assessing psychopathy in adulthood—to assess two incarcerated youth identified by clinical staff as demonstrating features of adolescent psychopathy. Consistent with the views of clinical staff, the PCL:YV and CAPP-IRS ratings indicated the presence of serious psychopathy-related personality disturbance in both cases. The PCL:YV and CAPP-IRS also revealed between-case differences in the specific nature or features of personality disturbance present, despite similarities in the overall level or severity of personality disturbance. Raters found it was relatively easy to administer the PCL:YV and the CAPP-IRS, although they identified some challenges, particularly with respect to the assessment of disturbance of self functions. Relative to the PCL:YV, which may be considered the gold standard for assessing the PCL:YV, the CAPP-IRS had some strengths and limitations. We discuss these findings in light of the literature on assessment of adolescent psychopathy and consider their implications for future research.