Prior research showed that online reviews have become an important factor for consumers to purchase products or services as a new element in marketing. Based on the Accessibility Diagnosticity Model and Regulatory Focus Theory, this research investigates the effect of different online review sources on brand evaluation and purchasing intention. Two experiments were proposed to examine the moderating role of self-regulatory focus and mediating role of perceived diagnosticity on the relationship between online reviews and consumer behavior. The findings indicate that when consumers are in the promotion-focused state, ordinary consumer reviews are more effective than expert critics to leads more brand evaluation and purchasing intention; whereas those in the prevention-focused state, expert critics are more effective than ordinary consumer reviews to produce favorable brand evaluation and purchasing intention. The outcomes occur because fit enhances perceived diagnosticity that account for the mediating role in the relationship between online reviews and brand evaluation and purchasing intention. The study integrates theories in different fields and broadens our understanding of the impact of online reviews from different sources on consumers, and the research conclusions have implications for how marketers manage online reviews.