Background: Treatment-resistant major depression (MDD) and obsessive-compulsive disorder (OCD) remain a major cause of suffering and disability. These disorders may be treated with functional neurosurgery that almost always is bilateral but some patients might benefit from unilateral procedures. Methods: We performed a unilateral right anterior capsulotomy (AC) in a 45-year-old right-handed woman with MDD and comorbid OCD. This unilateral procedure was based on the results of neuropsychological testing and an 18-Fluorodeoxyglucose positron emission tomography (FDG-PET) that revealed right hemisphere deficits in this patient. Results: Following surgery, Hamilton Depression scale (HAM-D) decreased 57% at 1 and 2 years and 54% at 3 years and Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) decreased 58% at 1 year, 77% at 2 years, and 96% at 3 years. There was a slight decrement of verbal memory and phonemic fluency after the procedure that could also be related to changes in medication. Right basal ganglia abnormalities revealed by FDG-PET remained unchanged 16 months postoperatively. Conclusions: Overall this unilateral right AC was effective for the treatment of this woman's disorders with minimal adverse side effects. © 2011 Copyright 2011 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business.