Rationale, aims and objectives: Children are not just small adults; they need to be diagnosed and treated in the context of their rapid growth and development. However, in guideline development, children's needs and interests are still overlooked. This study aims (1) to develop a tool that could stimulate guideline developers to take children into account on a more structural basis and (2) to explore how to facilitate children's participation in the process of guideline development. Methods: The method used was a three-phase multimethod sequential design. Professionals involved in guideline development participated in interviews (n = 12), filled in a questionnaire (n = 60) and/or participated in the focus group meeting (n = 11). Results: This study results in a comprehensive understanding of the considerations that professionals take into account when deciding whether guidelines need to apply to children specifically. This resulted in a tool that assists guideline developers to make this assessment more accurately. It takes the form of a flowchart that guides users through a series of critical questions. Conclusions: The flowchart reminds guideline developers to consider children as a particular patient population when prioritizing and demarcating new guideline topics. It will help to ensure that clinical guidelines address children's unique health care needs and perspectives. Facilitating children's and parents' participation in the process of guideline development is perceived as challenging; nevertheless, it should be the next step in making paediatric guidelines more child-centred and family-centred.