The diffusion of mobile devices such as tablet computers and smartphones enabling respondents to participate in self-administered online surveys create new challenges for survey methodology in terms of measurement (e.g., equivalence of mobile versus traditional online instruments) and nonresponse issues (e.g., response patterns among mobile participants in comparison to desktop-based respondents). By merging available data from several online access panel studies conducted between March and May 2012 in Germany, we have addressed four nonresponse-related research questions. First, how large is the share of mobile participants when conducting online panel surveys overall? Second, how can the propensity to choose mobile modes be explained? Third, do mobile participants differ on participation parameters, such as the number of completed questions, and the length of entries to openended questions? Fourth, does mobile participation change as more advanced technological features (such as Flash technology) are being embedded? The results to be presented show that 1) a considerable share of online panel members did participate using a mobile device, 2) that the propensity for choosing mobile devices to participate in online surveys is a function of age and gender (younger subjects and males are more likely to participate in this way, rather than older subjects and women), 3) mobile respondents did not substantially differ from traditional online survey respondents on an array of participation rate indicators. However, when using Flash technology, 4) mobile participants showed extraordinarily high dropout rates (about twice as much mobile drop-out rate when using Flash technology compared to traditional computers). Implications for survey methodology will be discussed, along with avenues for future research.