A recent large-scale randomized controlled clinical trial, the Clinical Antipsychotic Trials of Intervention Effectiveness-Alzheimer's Disease study, found a significant worsening of cognitive functioning in a sample of patients with Alzheimer's disease. To date there have been no equally powered studies examining the cognitive effects of atypical antipsychotics in patients with dementia with Lewy bodies, the second most prevalent neurodegenerative disorder. This case report describes a significant cognitive improvement observed through the use of an atypical antipsychotic in a patient with dementia with Lewy bodies. The observed divergence in cognitive responsiveness is discussed mechanistically on both the clinical and neuromolecular level. Limitations to this case study design are presented and discussed. The prudence of caution in importing the results of the Clinical Antipsychotic Trials of Intervention Effectiveness-Alzheimer's Disease study to the dementia with Lewy bodies population is summarized and presented for psychiatrists, neurologists and primary care providers, with an intent to stimulate discussion and further research.