Between 1908 and 1940, 431 young girls between 16 and 21 years of age were enrolled at Vejstrup Re-education Home for Girls. Through close readings of individual case records and other archival material from Vejstrup Re-education Home, this PhD thesis explores the ways in which the so-called “particularly difficult young girls” were perceived as problematic and how they were handled from 1908 to 1940. The thesis uncovers how the problematisation and handling of the girls changed as psychiatric knowledge was integrated into the field. The thesis is informed by Michel Foucault’s perspective on power and knowledge as mutually constitutive and on power as a productive force that transforms human beings into (specific kinds of) subjects. Introducing the concept of motherly caring power, the reform practices at Vejstrup Re-Education Home are analysed as a specific type of disciplinary liberal government directed at the individual’s will and emotions. The central technique used to re-educate the young girls was the relationship between the headmistress and each individual girl. The aim of re-education was ultimately to lead the girls to regulate themselves to become ‘good girls' and ultimately to strive for becoming servants and wives.The perception of child welfare was that every child could be re-educated, however 4.2% of the children and youth released from Danish residential care between 1905-1940 and 11.4% of the young girls released from Vejstrup Re-Education Home in the same period were released because they had been deemed incorrigible. The expulsions on the grounds of incorrigibility, led to a new problematisation and category that also comprised a new subject: The Incorrigible. During the 1920s, doctors became increasingly involved in assessing the nature of the girls at Vejstrup Re-Education Home, as well as in evaluating how they should be handled. The analysis shows that diagnoses, particularly the diagnosis psychopathy, grew intertwined with the existing category of incorrigibility. The reformulation of incorrigibility to psychopathy and other diagnoses was relevant, because the diagnoses entailed new ways of handling, as well as the anticipation of additional resources. In the 1920s the headmistress attempted to gain ressources for a closed ward at the institution, but did not succeed. In 1930 the subsequent headmistress initiated lobbying for the establishment of a psychopathic institution for girls in 1930. Though she did not succeed, doctors and politicians supported the idea, and a commission was formed to prepare a proposal for the establishment of a psychopathic institution. The thesis uncovers how the problematisation of so-called incorrigible girls as psychopaths emerged at Vejstrup Re-Education Home. Thus the thesis shows how child psychiatry was shaped and practiced within child welfare before the opening of the first Danish child psychiatric clinic in 1935 and before the 1958 establishment of a pedagogic committee in child welfare, incorporating e.g. professional knowledge from psychiatry and psychology.