Lewy body dementia (LBD) is the second most common form of dementia after Alzheimer disease. Clinical symp-toms include acute onset of cognitive fluctuations accompanied by dementia, visual hallucinations, disorientation and sleep disorders that suggest initially the diagnosis of delirium. Antipsychotic medication for the treatment of delirium worsens the symptoms due to neuroleptic sensitivity associated with increased morbidity and mortality patients with LBD. In literature, there are rare case reports with overlooked LBD that presented like delirium symp-toms. Additionally, it was declared that quetiapine and cholinesterase inhibitors have individually efficacy on treat-ment of LBD. In this case, we present a woman who had difficulty for diagnosis due to misdiagnosis of LCD and treatment with quetiapine and rivastigmine.