Self-esteem and self-concept seem to be very important in the development of drug use and abuse. Thus the major objectives of this study were to explore these two psychological variables in the group of drug-addicted adults (currently involved in treatment) and the group of students. Gender, duration of treatment, employment etc. influences were investigated in the group of patients. We also compared this group to the group of faculty students. We used the statistical methods included in the statistical package for social sciences. We found some statistically significant differences between the groups on both measures (self-esteem and self-concept), some indication of positive contribution of longer treatment in the group of drug-addicted adults and some gender differences in this group also. These results can be used in the drug-addiction treatment and open several questions for further research.