The aim of this study was to investigate the nature of substance dependency in relation to attachment styles, anxiety, perceived social support and self-efficacy. This is a correlational survey study, which is quantitative in nature. A cross-sectional between-groups design is used to investigate the differences between a clinical (N=33) and a non-clinical sample (N=41). The predictor variables include the attachment styles, anxiety, perceived social support, self-efficacy, and parental drug abuse and the criterion variables include levels of drug dependence and age of onset of drug use. Questionnaires including The Leeds Dependency Questionnaire (Raistrick et al, 1994); The Relationship Questionnaire (Bartholomew & Horowitz, 1991); The Beck Anxiety Inventory (Beck, 1988); The Multidimensional Scale of Perceived Social Support (Zimet et al, 1988) and The General Self-efficacy Scale (Schwarzer & Jerusalem, 1993) were applied to 74 participants. The results showed that there was a significant relationship between attachment styles and substance dependence. Anxiety levels were also significantly positively correlated with substance dependence. The non-secure attachment styles of preoccupied and dismissive-avoidant attachment were significantly related to the age of onset of drug use. An ANCOVA showed that there was no significant relationship between attachment styles and perceived social support in relation to substance dependency. There was also no significant relationship between attachment styles and self-efficacy in relation to substance dependency. The findings from this study suggest that among those with a non-secure attachment style, higher levels of perceived social support may lower levels of drug dependency. Fearful-avoidant individuals with drug dependency should be identified as individuals that require treatment that aims at enhancing self-efficacy. This study points to several clinical implications regarding assessment and treatment for patients with non-secure attachment styles. A number of strengths and weaknesses are also mentioned within. Future research is suggested to investigate the relationship between attachment styles and treatment outcomes. In conclusion, the attachment theory provides a unique way of classifying individuals which enhances knowledge on the complex nature of addiction.