This article discusses the social consequences of the impossibility of specifically defining the boundaries of the concept of mental disorder, which seems to be a “vague” term with no satisfactory definition, especially when referred to children’s behaviors. We argue that when discussing children’s problematic, disturbing or non-conforming behaviors it is necessary to understand how these concepts are related to the classificatory categories of children’s behaviors and presented as care demands, whether in common sense or in biomedical discourses. Data were collected in qualitative research developed in three different child mental health services (CMHS), one in Santos (2012) and two in Campinas (2009-2010; 2017-2018), Brazil. Based on what seems to be a relation between biological-psychological dysfunction and social-cultural expectation or response, our starting point is that agitation is also a multidimensional and vague category, presenting a description and theoretical reflection about the various concepts regarding agitation. The analysis focuses on the different uses of the concepts of agitation; the social actors and institutions involved in care demands and how they are interdependently connected; then revealing, from a sociocultural perspective, the implications of classifying and defining children’s behavior from this vague category.