AIMS: To establish the personality traits and disorders of pathological gamblers in treatment by means of a descriptive cross-sectional study of two prospective matched-pair cohorts: 50 pathological gamblers versus a control group of 50 normal volunteers (non-patient and non-pathological gamblers). All the pathological gamblers of the sample followed treatment as out-patients in the province of Valencia (Spain-EU). Recruitment period: January-May 2004. MEASURE INSTRUMENTS: South Oaks Gambling Screen, Barratt Impulsivity Scale, Sensation Seeking Scale, and Structured Clinical Interview for Personality Disorders of Axis II of DSM-IV. FINDINGS AND CONCLUSIONS: Male pathological gamblers go more often to health and social care facilities. Pathological gamblers prefer to play slot machines, present a higher prevalence of personality disorders, most of them belonging to cluster B, are more impulsive and higher sensation seekers than the controls. There are no linear relationships between the severity of pathological gambling and the traits of impulsivity and sensation seeking respectively.