The aim of the present study was firstly to describe the characteristics of alcoholic outpatients (A) suffering from co-morbid personality disorder (PD) of either the cluster B (A+PDB) or cluster C (A+PDC) type. Secondly, to investigate the effect of various kinds of treatment to be able to single out the most beneficial therapy. Thirdly, to identify the most beneficial treatment. The patients were offered the following outpatient treatments: cognitive behaviour therapy, family therapy and supportive consultations. The material consisted of 363 patients who started psychosocial treatment at the outpatient alcohol clinic at Odense University Hospital, Denmark. It was possible to re-interview 276 (76%) patients 1 year after onset of treatment. Of the 363 patients, 87% were alcohol-dependent (ICD-10) and 34% fulfilled the ICD-10-R criteria for PDs. The basic interviews focused on the seven main areas of the Addiction Severity Index. A+PDC had significantly more serious medical problems than A-PD, while the A+PDB group had significantly more employment, drug use and social problems than the A-PD. As for psychiatric status, A-PD had significantly different scores compared with A+PDB and A+PDC. A+PDB were younger and had a longer history of alcohol abuse than A-PD and A+PDC. After treatment there was no significance between the patients with and without PD concerning alcohol outcome and psychosocial outcome. The significance of co-morbid PD for the prognosis of alcohol abusers may be overestimated. Our results indicate that A+PD can be treated as successfully as other patients in an outpatient alcohol clinic can.