Health information systems (HISs) have been shown to introduce unintended consequences post implementation. Much of the current research on these consequences has focused on the negative aspects of them. However unintended consequences of HIS usage can also be beneficial to various aspects of healthcare delivery. This paper uses several case studies of HIS implementation to develop a model of unintended benefits of HIS usage with three categories of benefits: patient, service delivery and administrative. We also discuss the implications of these benefits on the design and evaluation of HISs.