INTRODUCTION: Psychiatric disorders are known to occur frequently in chronic epilepsy. The aim of this study is to investigate the prevalence of psychiatric comorbidity and its relationship to regional cerebral dysfunction in patients admitted to a tertiary epilepsy center for epilepsy surgery. METHODS: 217 patients were investigated. A presurgical workup was performed and allowed precise localization of the epileptogenic focus in 156 patients. Sixty-one patients had multifocal or generalized discharges. After 1-3 psychiatric interviews, a psychiatric diagnosis was made (DSM-IV classification). RESULTS: Psychiatric comorbidity was found in 85 patients (39%), more often in those with right or bilateral hemispheric dysfunction (74%, p = 0.04) with no difference between temporal or extratemporal foci location frequency. Additionally, patients with psychiatric disorders were less likely to undergo epilepsy surgery compared to 'epilepsy-only' patients (p = 0.003), despite similar good outcome in patients with and without psychiatric comorbidity. CONCLUSIONS: Right-sided or bilateral foci seem to represent a risk factor for psychiatric comorbidity in epilepsy, although we did not find any particular association between a psychiatric syndrome and focus localization. Recognition and treatment of psychiatric comorbidity is of major importance since its presence may interfere with patient's decision making for epilepsy surgery treatment.