A 34-year-old woman with a 9-year history of unprovoked attacks of anxiety and dyspnea associated with symptoms of depersonalization and derealization is presented. The attacks increased in frequency and were associated with internal derogatory voices, vivid frightening imagery, and suicidal ideation, leading to 3 emergency psychiatric hospitalizations in a period of less than 3 months. She had been treated unsuccessfully for a presumptive diagnosis of panic disorder without agoraphobia, prompting a reconsideration of this diagnosis. Although electroencephalography and magnetic resonance imaging findings were normal, temporal lobe epilepsy was considered and the patient responded rapidly and dramatically to carbamazepine. Panic disorder and temporal lobe epilepsy can be confused with each other; proper diagnosis is necessary for selection of effective pharmacotherapy. Although uncertain, the contribution of sustained exposure to carbon monoxide as an adult may have contributed to the emergence of panic symptoms, which would be an unusual clinical presentation.