In the 19th and early 20th century, psychiatric hospitals served as the main institution of mental healthcare for individuals with severe mental illness as well as a care center for the homeless and needy population. On the other hand, provision of mental health services has been transformed from the institutional-based services to the community-based services as a result of deinstitutionalization movement in the policy of mental health. The term of deinstitutionalization in mental health policy can be defined essentially as that the closing down and downsizing of large psychiatric hospitals and the introduction of smaller mental health care centers within the community. As well as in the most of the Western European countries including Germany, France, and the United Kingdom, the scope of psychiatric hospitals has been restricted in the United States and other Western countries i.e. Italy and Spain since the 1960s. On this regard, today, the type of mental healthcare provision can be divided into two sections; inpatient & residential care and outpatient care. While the inpatient & residential care includes mental hospitals, psychiatric wards, and community-based residential care facilities, outpatient care involves hospital outpatient departments, mental health outpatient clinics, community mental health centers (CMHC) including day-care treatment centers. In this paper, the main focus is about different ways of deinstitutionalization in three selected countries; in the United States, in the United Kingdom, and in Italy, respectively. In this point, what are different ways of deinstitutionalization in mental healthcare provision constitutes my core research question in this article.