Mobile phone surveys are gaining popularity, however very little experimental research has been conducted on mobile phone surveys. One rare exception is the work by Peytchev and Hill (2010), who embedded several experiments within a series of mobile surveys. In this study, we build on and extend Peytchev and Hill’s work in several ways: 1) by utilizing a large, national sample of mobile phone users, 2) by including an additional set of question wording and question formatting experiments, and 3) by conducting a parallel set of online survey experiments. The main focus of this study is replicating the experimental mobile survey findings with web surveys taken on a PC. The study design will allow us to compare findings between smartphone and online survey administrations. This study is based on 1500 online panelists who are also smartphone users. Respondents were randomly assigned to 1 of 4 survey versions: mobile version A, mobile version B, online version A, or online version B. Surveys for each study group were 25 questions and approximately 10 minutes long. Experiments embedded within the surveys included the presentation of low versus high frequency scales and closed-ended versus open-ended other categories (similar to Peytchev and Hill) as well as the manipulation of text box size and response option order. Finally, we also analyze survey breakoffs within and across modes, but study this observationally, rather than by explicitly manipulating length of survey. By conducting this research, we gain a better understanding of what does and doesn’t work with mobile surveys and how they can be optimized.