Online product reviews on commercial websites have been extensively studied as a form of electronic word-of-mouth (eWOM). There are some studies on eWOM in social media websites as well, however, little is known about the differences between eWOM on commercial websites and eWOM on social media websites. This research compares product reviews on Amazon.com, a leading online retailer website, and Reddit.com, a social media website with a specific culture, emphasizing on anonymity and free speech. Emotion, cognition, and deception present in the reviews were examined based on the Elaboration Likelihood Model of Persuasion and Interpersonal Deception Theory. It was hypothesized that positive affect, cognition, and deception levels are lower in reviews on social media websites than in reviews on online retailer websites. Results showed that reviews on Reddit.com have less words in positive affect as well as cognition than those on Amazon.com; no specific pattern was found about deception. Implications about different persuasion and marketing strategies on the two types of websites, as well as possible benefits to consumers are discussed.