Nicotine & Tobacco Research

the rise of user-generated content makes it particularly difficult to restrict protobacco messages (Ribisl, 2003). Previous studies have found that protobacco content on the Internet is perva-sive and easily accessible to youth (Hong & Cody, 2002; Ribisl, 2003), including popular websites, such as YouTube (Forsyth & Malone, 2010; Freeman & Chapman, 2007). YouTube is the third most-visited website worldwide and the fourth most visited in the United States (Alexa, 2010), allowing millions of users to create, watch, and share videos. U.S. viewers represent more than one fifth of all viewers on You-Tube. According to statistics from an August 2010 report by Nielsen Netview posted on YouTube’s website, more than half (51%) of U.S. Internet users have accessed YouTube and youth aged 2–24 years old make up 27 % of YouTube visitors. Among people who use the Internet in the United States, a dispropor-tionately high proportion of adolescents (12–17 years old) and young adults (18–24 years old) have visited YouTube (61% and 62 % of Internet users, respectively) compared with older adults (YouTube, 2010a). YouTube clearly has a strong appeal to youth and young adults, who are frequently the target audi-ence for tobacco companies and are particularly susceptible t