The study of psychopathic traits in youth is in its nascent stages and the nature and the structure of these traits is still poorly understood. In one of the most comprehensive analyses to date of the construct validity of the widely used Antisocial Processing Screening Device (APSD), we used two independent samples of youth, one community (N = 2203) and one clinic-referred (N = 534), ages 4 to 19 (51% female), to investigate the external correlates of the Callous-unemotionality (CU), Narcissism, and Impulsivity dimensions of youth psychopathy. We used parent reports of externalizing and internalizing psychopathology, personality, and aggressive behavior to examine the pattern of associations between psychopathic trait dimensions and relevant external correlates. Across both samples, CU was positively related to all forms of externalizing psychopathology and aggression, mostly unrelated to internalizing psychopathology, and negatively related to agreeableness and conscientiousness. Narcissism and Impulsivity were positively related to externalizing psychopathology, and aggression, negatively related to agreeableness and conscientiousness, and weakly positively related to internalizing psychopathology. In most cases, each dimension of the APSD manifested statistically significantly different relations with these external correlates. Many of our findings replicate and extend work conducted with both youth and adults, although others suggest that these dimensions do not distinguish among psychopathological domains in conceptually expected ways. Broadly speaking, these findings provide evidence that psychopathic traits in youth are best characterized by a multidimensional model and bear implications for models integrating normative with pathological personality. (PsycInfo Database Record (c) 2020 APA, all rights reserved).