This study examined youth reactions to four tobacco countermarketing messages from the national truth^® and “Think. Don't Smoke” tobacco countermarketing campaigns through Web TV using a forced exposure approach. More than 900 respondents completed a baseline survey that established their smoking intentions and behaviors; viewed a series of randomly ordered tobacco countermarketing advertisements; and, after each ad, answered six items gauging individual ad reactions. Respondents across smoking risk groups had more favorable reactions to two ads produced for Legacy's truth^® campaign (“Body Bags” and “Daily Dose”) compared with all other messages tested. Philip Morris' “My Reasons” received favorable evaluations among teens at lowest risk for future smoking, but consistent with our predictions derived from the theory of psychological reactance (Brehm, 1966), older teens at elevated risk of future smoking responded much less favorably. Teens without prior exposure to another truth^® ad using the counter-industry message (“Shredder”) rated this ad less favorably. Results underscore the importance of both prior exposure and message features and suggest the presence of other factors associated with ad effectiveness, including message clarity and stylistic presentation.