Assessment of psychopathology in Huntington's disease (HD) using formal DSM-IV criteria is complex because of comorbid somatic and cognitive disturbances and diminished disease awareness. Using dimensional tests in 152 HD mutation carriers, both the total score of the Problem Behaviors Assessment (PBA) scale and the behavioral section of the Unified Huntington's Disease Rating Scale (UHDRS-b) corresponded with presence of DSM-IV diagnoses. Receiver operating characteristic curves showed an area under the curve of 0.87 for the PBA and 0.91 for the UHDRS-b, demonstrating moderate to strong discriminatory power. Using caregiver information, subjects who were too cognitively impaired for composite international diagnostic interview assessment showed similar high PBA and UHDRS-b scores, with both a negative predictive value of 96% and a positive predictive value of 40% and 44%, respectively, for the presence of formal psychiatric disorders, indicating that dimensional rating scales and caregiver information allow for the assessment of psychopathology in advanced-stage HD.