The parental relationship in ECEC (Early Childhood Education and Care) service forms a key factor for its quality. This relationship is also complex and problematic and can be understood in different ways. There is a lack of research about the parental relationship in ECEC compared with schools. However, some researches have revealed the importance of a functional parental relationship in ECEC but also that the relationship can challenge the professional task of the teachers. One way to understand the parental relationship is study it out of two different frameworks, a vertical or horizontal framework. The vertical framework regards the teachers as experts and with asymmetrical, involved or engagement parental relationship. The horizontal framework regards both teachers and parents as experts and with a symmetrical partnership parental relationship. This review of research has scrutinised how the parental relationship in ECEC is described based on a division into levels as parental involvement, engagement or partnership relation. All three levels were identified in the 22 articles studied, but with a slight domination of the parental partnership. Four advantages of the parental relationship have been identified, quality-indicator, empowerment of parents and teachers, impact on future student academic achievement and flexible relationship. Three problems have been identified, different roles of parents and teachers, discrimination and complex relationship. One conclusion is that the parental relationship is of great importance to the ECEC service, but that it is more realistic to consider this as a balance between vertically and horizontally-framed parental relationships in ECEC services.