Pleasantness evaluations and preferences related to odors have traditionally been thought of as rather inflexible. An increasing number of empirical studies reveal, however, some evidence of flexibility. This thesis sought to examine how and to what extent decision-making processes can shape olfactory preferences, as well as the level of processing required in such a choice-induced preference modulation (explicit vs. implicit) and how long the modulation persists. In the empirical part of this thesis, we present empirical evidence demonstrating that (i) olfactory preferences can indeed be shaped by decision-making processes, (ii) this shaping does not require explicit processes, and (iii) the change can be long-lasting. These results invite further consideration of the modulatory impact of decision-making processes on olfactory preferences and of the importance of implicit processing in olfactory preference modulation and stability across time. The theoretical implications of these results, in particular regarding cognitive dissonance theory, are discussed.