In this paper, we apply the theory of task technology fit to information systems that are used by mobile professionals. We describe the results of an empirical study of 216 users of mobile devices that included various smart phones, personal digital assistants (PDAs), and laptop computers. Our findings suggest that (1) the relationship between task difficulty and functional requirements of the mobile devices is stronger for highly mobile users than for less mobile users; (2) user mobility is associated with increased user-perceived importance of a number of nonfunctional features; and (3) for a number of functions and features, highly mobile users indicated a stronger relationship between task-technology fit, and overall evaluation of the technology. We conclude that user mobility needs to be taken into account when applying the theory of task-technology fit to mobile information systems. In addition, our study provides specific insights about the information system requirements of mobile professionals.