Equivalence is a necessary prerequisite of any substantive analysis of cross-cultural survey data. Cognitive interviewing is a suitable method when it comes to identifying non-equivalence in survey data and, particularly, its causes. Usual face-to-face cognitive interviews have their shortcomings or particular challenges, though, such as limited sample sizes, great time and cost investment, or interviewer effects due to different interviewer behavior. In cross-national research, these problems are exacerbated and, thus, it does not come as a surprise that the use of cognitive interviewing in the comparative context brings with it particular challenges. We therefore propose to test web surveys as a supplemental means to conduct cross-cultural probing studies and to assess equivalence of measures in cross-national studies. Web surveys permit to counter the above mentioned aspects: they allow e.g. the cost-effective increase in sample size and therefore quantification of results; they also allow for the standardization of probing procedures, a factor which is not unimportant in cross-national studies. In this paper, we report findings regarding equivalence from an international web survey conducted in Canada, Denmark, eastern and western Germany, Hungary, Spain, and the US in January 2011. A net sample of 480 respondents in each country/region was targeted. Online access panels were commissioned to provide the respondents according to pre-set quotas. The survey on politics and family included eight probing questions for each respondent, among which category selection probing, comprehension probing, and specific probing. Among the close-ended questions, four items regarding beliefs on immigrants taken from the ISSP 2003 questionnaire on “National Identity” were asked in the survey. They refer to whether immigrants increase crime rates, whether they are generally good for the economy, whether they take jobs away from native people, and whether they improve society by bringing in new ideas and cultures. Four splits were implemented and each of the four items figured as the first item in one of these split version. In each split, the first item was followed by a specific probe, which was: “Which type of immigrants were you thinking of when you answered the question?” Being aware that design plays an important role in web surveys due to its impact on answer behavior, we additionally implemented a design experiment for the above mentioned probe. Respondents were thus randomly assigned either to a probe with a small answer box or a probe with a large answer box in order to test the effect of answer box sizes on answer patterns.