Mobile advertising is gearing up for success, but researchers and practitioners need to understand how to measure the effectiveness of this advertising form—particularly the factors that drive mobile messages home in different cultures. This study identifies key measures of effectiveness as well as antecedent variables in the context of 629 Korean and American consumers. Entertainment and credibility were key factors predicting positive attitude and purchase intention among both Koreans and Americans. However, this study found multiple cross-cultural differences—particularly in informativeness, perceived interactivity, and the value of mobile advertising. Theoretical explanations and practical implications are suggested. © 2008 Wiley Periodicals, Inc.