To date, research into personality traits among gamblers has been largely inconsistent. The purpose of this study was to assess the predictive values of three personality traits on pathological gambling (sensation seeking, deferment of gratification and competitiveness) never been investigated before. A questionnaire was administered to 114 gamblers of whom 38% were classified as pathological gamblers according to the DSM-IV criteria. The questionnaire included the Sensation Seeking Scale (Zuckerman, M. (1984). Sensation seeking: a comparative approach to a human trait. Behavioural and Brain Sciences, 7, 413-471.), the Deferment of Gratification Scale (Ray, J.J. and Najman, J. (1986). The generalisability of deferment of gratification. Journal of Social Psychology, 126, 117-119.) and the Gambling Competitiveness Scale constructed by the authors specifically for this study. Results showed that competitiveness had a strong positive predictive value for pathological gambling, and that deferment of gratification had relatively strong negative predictive value. Sensation seeking was shown not to be a significant predictor of pathological gambling. This is the first ever study to show empirically that competitiveness and deferment of gratification appear to be important risk factors in pathological gambling.