The aim of the study is to identify criteria that frail elderly patients refer to when they appreciate the quality of care of Geriatric assessment units. Twenty-one patients recently released from six Geriatric assessment units in Montreal participated in face-to-face interviews (n = 17) or in a Focus Group (n = 4). Patients reported 56 different criteria grouped into four main dimensions of quality: the environment of care, the attitude and the technical competence of professionals and the results of care. The environment of care consists of physical resources and person related qualities. Comments on the attitude and the technical competence of professionals related mostly to the nurses and physicians. Some quality criteria reported by elderly patients are similar to those reported by patients in various acute care units while others are specific to the frailty of their condition. This study provides health care professionals with rich and useful information on how elderly patients perceive the quality of various components of care in Geriatric assessment units.