The authors investigate the determinants of CIOs' organizational role and tasks. They first review previous studies, which they classify as either evolutionary or CIO role studies. They consider them to be characteristic to the usage of certain technologies or certain periods of times. The authors modify Leavitt's well-known organization diagnostic model to describe factors that shape the role and the tasks of CIOs over time, industries and technologies. They validate the model from interviews with 36 CIOs within six industries covering the time period from 1960s to present times. The authors also show that the model can be used to categorize prior research findings. They then use the model to describe how technology influences business strategy and how business strategy and technology impacts CIOs' role and tasks and vice versa. The authors discovered that the modified Leavitt model is a useful description of factors that both define CIOs' role and tasks at any particular time in any specific organization, and show how those tasks change.