A growing number of people access the Internet via a mobile device. Among this group are people who go online mostly using a mobile device or only using a mobile device. Survey organizations must now consider whether to use this technology to survey the general population. Yet low penetrations rates--45% of U.S. adults still do not have mobile-Web access --raise concerns about the coverage bias for substantive variables that would result if only the mobile-Web population were surveyed. Meanwhile, the growing mobile-only population raises concerns about coverage bias for traditional Web surveys that exclude these users. Using 2012 data from the Pew’s Health Tracking Survey, we first explore the correlates of noncoverage for surveys designed only for mobile-Web users. Next using 2012 data from Pew’s Spring Tracking Study, we explore correlates of noncoverage for traditional Web surveys that exclude mobile-only users. In our multivariate models, we expect to find significant demographics differences in Internet access via a mobile device, as others have found. We will also check for differences in health status and self-reported quality of life. Even after controlling for demographic differences in mobile-Web access, it is possible that substantive variables will show significant associations with mobile-Web access. These findings will shed light on whether researchers using either a mobile-Web sample or a Web sample that excludes mobile-only users can correct all of the bias of differential mobile-Web access by weighting on multiple demographic characteristics.