Patients leaving inpatient psychiatric care without informing staff can have serious consequences for patient welfare, their families and staff. Even in cases where there are no serious outcomes and patients return, treatment can be interrupted and staff morale compromised. Given these potential deleterious effects, it is important to have an in-depth understanding of why people leave when they do. The aim of this study is to examine the profile of service-users who leave in-patient psychiatric care without notifying staff and to determine their reasons for doing so, what they did when they left the hospital setting and reasons for returning. This is a prospective descriptive study of service users leaving without notifying staff from a national mental health service in Ireland. It investigated the frequency, timing, and motivations of these absconding events among a sample of in-patients over a 12-month period. This year-long review identified 75 episodes of leaving without notifying staff, 55 of which met this studies criteria. 22% of episodes were from a locked unit, 58.2% were repeated episodes. 89% of service users returned to hospital following the episode and 11% were discharged against medical advice. Although no fatalities, three service users were seen in an emergency department as a result of activity during leave. Upon return from leave, all service users were reviewed and their care plans were updated where necessary.