Background:A large proportion of health promotion campaign evaluation research has historically been conducted via telephone surveys. However, there are concerns about the continued viability of this form of surveying in providing relevant and representative data. Online surveys are an increasingly popular alternative, and as such there is a need to assess the comparability between data collected using the two different methods to determine the implications for longitudinal comparisons. The present study compared these survey modes in the context of health promotion evaluation research. Methods:Data were collected via computer-assisted telephone interviewing and an online panel. In total, 688 and 606 respondents aged between 14 and 45 years completed the online and telephone surveys, respectively. Results:Online respondents demonstrated higher awareness of the advertisement, rated the advertisement as more personally relevant and had better behavioural outcomes compared with the telephone respondents. Conclusion:The results indicate significant differences between the telephone and online surveys on most measures used to assess the effectiveness of a health promotion advertising campaign. Health promotion practitioners could consider the combination of both methods to overcome the deterioration in telephone survey response rates and the likely differences in respondent outcomes.