AIMS: Detection of errors is crucial for efficient goal-directed behaviour. The ability to monitor behaviour is found to be diminished in patients with substance dependence, as reflected in decreased error-related brain activity, i.e. error-related negativity (ERN). The ERN is also decreased in other psychiatric disorders with impaired response inhibition, such as attention-deficit hyperactivity disorder and borderline personality disorder, but increased in anxiety disorders. The objective of the current study was to assess error monitoring in alcohol-dependent patients in relation to psychiatric comorbidity. We expected decreased error monitoring in alcohol-dependent patients with impulse control disorders and increased error monitoring in anxious alcohol-dependent patients. DESIGN: In a case-control design alcohol-dependent patients were compared with healthy controls. SETTING AND PARTICIPANTS: A consecutive series of 29 male alcohol-dependent patients, between 18 and 55 years of age, applying for in-patient detoxification were recruited at Novadic Kentron Center for Addiction Treatment. Fifteen age-matched healthy controls were recruited through advertisements in regional newspapers. MEASUREMENTS: Event-related potentials were recorded while performing a speeded choice-reaction task, from which ERN amplitudes were calculated. Axis-I and -II psychiatric comorbidity were assessed using the MINI International Neuropsychiatric Interview and the Structured Interview for DSM-IV Personality disorders. All participants completed the Temperament and Character Inventory and Profile of Mood States. FINDINGS: ERN amplitudes were increased for alcohol-dependent patients compared to healthy controls, particularly in patients with comorbid anxiety disorders. CONCLUSIONS: Increased error monitoring in alcohol-dependent patients, particularly those with comorbid anxiety disorders, is in contrast with previous studies that suggested decreased error monitoring to be a general feature in substance use disorders. Psychiatric disorders co-occurring with alcohol dependence, such as anxiety disorders, may indicate subpopulations of alcohol-dependent patients, with distinct neurobiological and genetic characteristics, possibly requiring different treatment strategies.