Objective: To determine the extent to which the Youth Self-Report (YSR) can be used to assess emotional and behavioral problems in adolescents with intellectual disabilities (IDs). Method: In 2003, 281 11- to 18-year-olds with IDs (IQ greater than or equal to 48) completed the YSR in an interview, and in 1993, 1,047 non-ID adolescents completed the YSR themselves. Parents completed the Child Behavior Checklist (CBCL). The ID sample was split into lower (IQ 48-69) and higher (IQ greater than or equal to 70) IQ groups. Cronbach's alpha values of the YSR scales and (intraclass) correlation coefficients between and within YSR and CBCL scale scores were calculated to determine parent-adolescent agreement and YSR construct validity, which were compared between samples. Mean YSR scale scores were compared between adolescents with ID with and without psychiatric symptoms. Results: Cronbach's alpha, parent-adolescent agreement, and indications of construct validity were about similar in all samples, although discriminant validity was somewhat weaker in the lower IQ group. Mean scale scores were 1.5 to 2.0 times higher for ID adolescents with psychiatric symptoms. Conclusions: The YSR seems applicable in youth with an IQ greater than or equal to 48. Further research is needed to refine and confirm these findings and the factor structure of the YSR in adolescents with ID and to differentiate between adolescents with moderate and mild IDs. (Contains 3 tables.)