IT addiction is a growing threat to quality of life and work performance. Online social networks, computer games and email are among the main culprits of such addiction. Surprisingly, the MIS literature has paid scant attention to this important area of research. An important limitation of past research is a focus that is too narrow to study the overall dynamics of IT addiction. My dissertation aims to elucidate these dynamics by incorporating multiple technologies and using a multi-method approach. Based on theories of reward and self-control, I will first define IT addiction and develop an instrument to measure it. I will then employ an experiment to validate the scale and to examine the effects of IT addiction on work performance. The results should pave the way for further academic inquiry into the nature of this ever-important construct, and should suggest practical measures to overcome its deleterious effects in the workplace