This chapter focuses on the interplay of cognition and cognitive feelings. The term cognitive feelings may appear surprising at first glance, because in daily language the terms feelings and affect are often used synonymously. The chapter selectively reviews evidence about how fluency may serve as information in judgments across all kinds of domains, including judgments about cognitive system, judgments about others, judgments about liking, and judgments of frequency, to name but a few. Fluency is a cognitive feeling and refers to the subjective experience of ease or difficulty associated with mental processing. Fluency is the subjective experience of ease or difficulty associated with mental processing. Fluency is linked to credibility; what is different is the source of fluency, which is either retrieval or understanding. Corroborating the fluency—truth hypothesis, research suggests that increasing processing fluency independent of repetition produces truth effects, too.