ABSTRACT The purpose of the following qualitative study is to investigate how social workers in the social services make decisions based on the application of law from the Convention on the Rights of the Child and the Social Services Act for children of school age up to 15 years, who have problems in their relationship with their guardians and who are exposed to an unsafe environment. Semi-structured interviews were conducted with four social workers. In the social services' child and youth investigations, the best interests of the child and the Convention on the Rights of the Child are considered in Article 12. The study wants to understand how social workers consider the best interests of the child in investigations and assessment of interventions. There are several different methods that are implemented in the social services' child and youth investigation. BBIC, Signs Of Safety and ACE. The methods are applied to help social workers to investigate those families with children where, for example, there is violence in a close relationship, neglect and where there are shortcomings in parenting. Interventions that the social worker offer are supportive interventions and intervention efforts. Important factors that can affect the assessment one of the efforts is health. Keywords: Sign of Safety, children social work, children mental illness, parental behavior affects children and parents' relationship to their children.