Although online surveys enable researchers to quickly and easily conduct advertising conversion studies, data obtained from online surveys are potentially problematic because of nonresponse bias. This study builds on earlier research concerning nonresponse bias in Internet-based tourism advertising studies using a number of different destinations across a number of years; in particular, this study uses the Propensity Score Adjustment approach to adjust for potential nonresponse bias in the collected data. The results of this study clearly indicate that online surveys generally result in relatively small errors when estimating conversion rates and various aspects of traveler behavior. However, this study additionally indicates that potential nonresponse biases are not consistent across advertising programs and survey waves, suggesting that destination marketers should put more effort into understanding response bias so as to represent the total target markets more accurately. To do so, destination marketing organizations and practitioners need to collect auxiliary variables that help to adjust potential nonresponse bias.