Background: The World Health Organization (WHO) published a clinical case definition of post COVID-19 condition, by a Delphi consensus, on 6 October 2021. That process concluded that a separate definition may be applicable for children. It is important to understand the frequency, characteristics and risk factors that lead to post COVID-19 condition, along with its impact on everyday functioning and development of children and adolescents. Long-term outcomes of the condition are currently unknown and need to be studied. For these reasons, a globally standardized clinical case definition is needed. Aim: To develop a globally relevant standardized clinical case definition for children and adolescents by building on the WHO clinical case definition for post COVID-19 condition in adults.