Research on deep brain stimulation (DBS) for treatment-resistant depression appears promising, but concerns have been raised about the decisional capacity of severely depressed patients and their potential misconceptions about the research. We assessed 31 DBS research participants with the MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR), a well-validated capacity measure, and with a scale to measure therapeutic misconception, which occurs when subjects do not recognize key differences between treatment and clinical research. Correlations with baseline depressive symptoms were explored. Subjects' performance on the MacCAT-CR was excellent, but therapeutic misconception was still apparent. A trend toward significance was found in the correlation between baseline depression ratings and total therapeutic misconception score. Responses to open-ended prompts revealed both reassuring and concerning statements related to expectations of risk, benefit, and individualization. Even severely depressed patients did not manifest impairments in their capacity to consent to DBS research. Therapeutic misconception, however, remained prevalent.