The technology acceptance model, and extensions of it, suggests a causal relationship between the perceived ease of use and usefulness of an information technology system. Using a dataset based on the responses from 247 undergraduate business students in relation to their use of an educational technology system, we compared competing structural equation models of technology acceptance. We found support for our hypotheses indicating that, while ease of use is important, it does not determine perceived usefulness. Task-technology fit is, however, a direct causal antecedent of perceived usefulness and this relationship is modified by perceived ease of use. The results of this study suggest that technology acceptance models may need to be revised to consider changes in users' perceptions and behaviour related to the use of mobile computing technology and current software development practices.