Search engine advertising has emerged as the predominant form of advertising on the Internet. Despite its increasing importance academic research on this topic is scarce. Several authors have called for more research on how the content of the ad influences its evaluation. This exploratory study builds on this call for more research and examines the impact of evidence type on click-through and conversion rates in a search engine advertising setting. We find that click-through rates are higher for advertisements involving expert evidence and statistical evidence than for advertisements involving causal evidence. On the contrary, we find that causal evidence results in higher conversion rates than other types of evidence. These findings help marketers to fine-tune their advertising in search engines. In particular, if their aim is to attract people to the website, expert evidence and statistical evidence should be used, while causal evidence works best if the main objective is to generate conversions.