A personality addiction hypoFinal Year Project is used to discover if personality traits are predictive of substance abuse. Target participants consisted of 25 individuals from the Ballymun methadone dispensing clinic and 25 individuals from the Ballymun job centre. The current study explored personality effects on addiction levels while controlling for peer use, family influences, education levels, sensation seeking qualities and impulsiveness. The Big Five Inventory (John & Srivastava, 1999) is used to measure personality while the Leeds Dependence Questionnaire is used to measure addiction. Multiple regression analysis shows the predictor variables have significant predictive values in relation to dependency levels. (Adjusted R Square = 0.0477, F(13, 35)=4.374, P<0.05). The 'intensity' aspect of sensation-seeking was shown to have a significant moderately strong effect on dependency levels (Standardised Beta = .296, p< 0.05).