The goal of mixed modes is to combine data from different sources. This assumes that data can be validly combined and that there is equivalence of measurement. Data from different modes may be different because the modes themselves lead to different response processes, or because radically different question formats are employed in different modes. For example, the visual presentation of response lists in self-completion modes (such as web surveys) and in face-to-face interviews with show cards, allow the survey designer to use long lists of response options. However, such lists are not feasible in telephone interviews relying solely on verbal communication. When accommodating for the restricted channel capacity of telephone surveys, designers often decompose response scales into two or more steps (unfolding or branching), while in modes that use visual presentation the full list of response categories is presented. In a series of cross-cultural experiments we investigated whether mode or question-format effects cause differences in response between telephone and web surveys, and how large these effects are. The same type of experiments was performed in the Netherlands, Germany, and the UK. In each experiment respondents were randomly assigned to one of two modes: a computer assisted telephone interview or a web survey. Within each mode the same split ballot experiments on question format (full scale in one-step vs. branching in two or three steps) were conducted. This design enables us to disentangle question format effects from ‘pure’ mode effects. Furthermore, it gives us the opportunity to investigate whether the findings are generalizable and replicate in different countries.