Valence, the concept that describes pleasantness or unpleasantness of events, is considered as a fundamental building block of our affective experiences. Although converging evidence suggests that valence should be viewed as multi-dimensionally represented, its finer structure remain controversial. This dissertation explores a possible affective and cognitive dissociation of the valence, namely affective valence and semantic valence. Affective valence refers to the internal feeling people experience, and semantic valence refers to factual knowledge about the valence of events. We collected data from multiple sources including behavioral, physiological and neuroimaging data to provide converging evidence of the dissociation and investigate the underlying mechanisms of and relationship between the two modes of valence. We found that people are able to dissociate between the two modes of valence with little training. Consistent with the conjecture that affective valence focuses on internal feelings and semantic valence requires more understanding of the stimulus, heart rate and eye-tracking data suggested more sensory intake during the evaluation of semantic valence. Moreover, the neuroimaging data revealed that the two modes of valence involve separable underlying processes. We found that affective valence engaged regions involving anterior cingulate cortex and anterior insula which are associated with emotional awareness, and semantic valence engaged regions involving inferior frontal gyrus, middle frontal gyrus and anterior temporal lobe which are linked to semantic memory.