Patients with obsessive-compulsive disorder (OCD) often only partially respond to serotonin reuptake inhibitors (SRIs), the first-line pharmacotherapy for OCD. The American Psychiatric Association's Practice Guidelines suggest augmenting SRIs with either cognitive behavioral therapy consisting of exposure and ritual prevention (EX/RP) or antipsychotic medication (e.g., risperidone) [1]. EX/RP has been shown to be more effective [2]. However, some patients prefer medications over EX/RP [3]. How should treating clinicians respond in these situations? Conventional wisdom would suggest that patients who prefer one treatment may not benefit if assigned to another. Indeed, meta-analyses of randomized controlled trials (RCTs) show that patients are less likely to improve and more likely to drop out when matched to a therapy condition they did not prefer [4]. However, this issue has never been investigated empirically for OCD treatment specifically. Therefore, we examined the effect of patient preference on outcomes in a RCT of SRI augmentation in adult OCD patients. We specifically compared the effectiveness of EX/RP in OCD patients who stated that they prefer risperidone, and vice versa.