The present article gives a critical overview of how the components N1, N2, especially the mismatch negativity (MMN), and P3 have been investigated and interpreted in the context of 'chemosensory event-related potential' (CSERP) research. In order to integrate the respective CSERP results, findings and theoretical models from other modalities are briefly described for each component. It is suggested that all components found so far within the CSERP strongly depend on the psychological state of the individual. In particular the dominant positivity of the CSERP has been focused on by investigating the specificity of olfactory emotional processing in comparison to emotional and neutral stimuli from the visual modality. The results reveal that the late positive complex within the CSERP consists of two subcomponents, one of which has a frontal and the other a parietal dominance. The posterior positivity seems to reflect the features of the P3 component and varies with the valence of odors, whereas the anterior positivity seems to be similar to the Novelty-P3. A link between olfactory and emotional processing has been confirmed by the finding that the P3 elicited by visual stimuli shows similar valence effects.