Barriers are defined as factors that prevent a child from having full and equal access to and participation in humanitarian assistance and protection. These can be environmental, including physical barriers (such as the presence of stairs and the absence of a ramp or an elevator) and communication barriers (such as only one format being used to provide information), attitudinal barriers (such as negative perceptions children with disabilities), and institutional barriers (such as policies that can lead to discrimination against certain groups). Some barriers exist prior to the conflict or natural disaster; others may be created by the humanitarian response.

The right of the child to have his or her best interests assessed and taken as a primary consideration in reaching a decision. It refers to the well-being of a child and is determined by a variety of individual circumstances (age, level of maturity, the presence or absence of parents, the child's environment and experiences). See Principle 4.

A formal process with strict procedural safeguards designed to determine the child’s best interests for particularly important decisions affecting the child. It should facilitate adequate child participation without discrimination, involve decision-makers with relevant areas of expertise and balance all relevant factors in order to identify and recommend the best option. (UNHCR Best Interests Determination Handbook 2011, p. 110)