Researchers used a quasi-experiment (N = 723) conducted in the field and using both pretests and posttests to carry out a theory-based evaluation of the effectiveness of a media literacy curriculum implemented in Washington state. Results showed that reflective thinking concerning media message about tobacco increased for all media literacy participants, whether or not they had used tobacco previously. Changes in reflective thinking affected a range of decision-making indicators. Lesson participants who had not used tobacco demonstrated greater change at earlier stages of decision making in ways that suggested a greater understanding of the persuasive techniques used by tobacco manufacturers, on indicators such as perceived realism, desirability, and similarity. Lesson participants who had tried tobacco demonstrated greater change at later stages of decision making on indicators such as perceived peer norms for tobacco use, identification with tobacco-related portrayals, and expectancies for tobacco use. All participants also showed increases in their ability and motivations to resist smoking-related influences. Overall, the results suggest that media literacy has important and somewhat different effects on those who have and those who have not experimented with tobacco use. The results also show the importance of measuring cognitive and affective indicators of decision making that may change gradually as participants gain experience putting lessons learned into action.