Information quality and system quality are considered key factors in determining the usefulness of systems. However, prior studies have yielded mixed results. This article holds that the system's assistance (the degree of the assistance provided by a system through its two roles: automating and informating) mediates in this relationship and may help to explain such mixed results. Furthermore, it holds that the system's level of intervention (the degree to which technology participates in carrying out the tasks) is another key factor in determining its usefulness, especially through the automating role. Data from 246 users filling different hierarchies and functional areas were collected. Results show that information quality and system's level of intervention explain usefulness through both roles. System quality explains usefulness through the informating role, but not through the automating role. The factors' differentiated effects through each role may help managers to establish more effective criteria and priorities in the different stages of an information system's life cycle.