The Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) specifier 'with Limited Prosocial Emotions' (LPE) is expected to provide information about impairment of adolescents with conduct disorder (CD) and to designate a severe subgroup of antisocial youths. This study is the first to scrutinize the clinical usefulness of this LPE specifier outside of a research context. Standardized questionnaires and diagnostic interviews were administered to 380 detained boys as part of a clinical protocol. Boys with CD that met criteria for the LPE specifier did not significantly differ from CD boys without LPE on any of the variables of interest. When using a CD diagnosis by itself (that is, without linking it to the LPE specifier) boys with CD were significantly more psychiatrically disturbed, rule-breaking, reactively and proactively aggressive, and reported more violent and nonviolent offenses than boys without CD. These differences were also revealed while using the LPE specifier by itself (that is, without linking it to a CD diagnosis). Additional analyses, nevertheless, showed that the magnitude of the group differences was strong when using a CD diagnosis by itself, but weak to moderate when using the LPE specifier by itself, or when incorporating the LPE specifier into a diagnosis of CD as recommended by the DSM-5. Altogether, this study suggests that incorporating the LPE specifier into CD is of restricted usefulness to discriminate between detained boys with varying levels of psychiatric problems and antisocial behavior. Interestingly, a CD diagnosis by itself seems the most clinically useful measure to identify a troubled group of detained boys.