We all need to resort to deception, either with ourselves (denial, self-deception, mystification) or with others (with modalities, such as impression management, social desirability), to a greater or lesser extent. Lies, in their broader meaning, are interpreted as something rather adaptive, useful, and necessary in our socioaffective world. In particular, self-deception is a highly interesting psychological concept in the clinical population, namely, in drug dependents, as it serves as a mechanism for maintaining addiction. The objective of this study was to create and explore the validity and psychometric properties of a short self-deception scale (SDQ-12), derived from the IAM-40 and emphasizing the manipulation and mystification dimensions. Participants in this study included a group of drug dependents (alcoholics and drug abusers) under treatment (n = 417) as well as a group of adults from the general population (n = 124) (total N = 541), selected using simple random sampling. Across the sample, 63% of individuals were male, with a mean age of 38.65 years (S.D. = 10.61). Empirical exploration of the SDQ-12 items using exploratory and confirmatory factor analysis revealed that the instrument has a clear structure matching the theoretically relevant proposed dimensions of mystification and manipulation. Internal consistency was verified (Cronbach's alpha coefficient = .85), and confirmatory factor analysis revealed that the two-dimensional model provided an appropriate fit to the data. In addition, manipulation was greater in young male individuals, with significant differences found in mystification and manipulation between the general population and alcoholics and drug abusers. Our study supports the clinical and research importance of the SDQ-12 scale, due not only to its diagnostic efficacy but also to its novel nature, its importance, and its relevance. It could be particularly useful for evaluating the substantial components of self-deception in the addict population, thus guiding therapists in their diagnostic and interventional role.