Informal and involuntary (compulsorily detained) patients are the two broad categories of patients in psychiatric hospitals today. In Rabone v Pennine Care NHS Trust the Supreme Court made, among other things, a distinction between the two types of patients. This article contributes to the literature by adding to that distinction. It looks at the evolution of the term, ‘informal patient’, gives an account of Rabone case and then deals with the comparison between the two types of patients.