The US FDA and the European Medicines Agency (EMA) have issued incentives and laws mandating clinical research in pediatrics. While guidances for the development and validation of patient-reported outcomes (PROs) or health-related quality of life (HRQL) measures have been issued by these agencies, little attention has focused on pediatric PRO development methods. With reference to the literature, this article provides an overview of specific considerations that should be made with regard to the development of pediatric PRO measures, with a focus on performing qualitative research to ensure content validity. Throughout the questionnaire development process it is critical to use developmentally appropriate language and techniques to ensure outcomes have content validity, and will be reliable and valid within narrow age bands (0-2, 3-5, 6-8, 9-11, 12-14, 15-17 years). For qualitative research, sample sizes within those age bands must be adequate to demonstrate saturation while taking into account children's rapid growth and development. Interview methods, interview guides, and length of interview must all take developmental stage into account. Drawings, play-doh, or props can be used to engage the child. Care needs to be taken during cognitive debriefing, where repeated questioning can lead a child to change their answers, due to thinking their answer is incorrect. For the PROs themselves, the greatest challenge is in measuring outcomes in children aged 5-8 years. In this age range, while self-report is generally more valid, parent reports of observable behaviors are generally more reliable. As such, 'team completion' or a parent-administered child report is often the best option for children aged 5-8 years. For infants and very young children (aged 0-4 years), patient rating of observable behaviors is necessary, and, for adolescents and children aged 9 years and older, self-reported outcomes are generally valid and reliable. In conclusion, the development of PRO measures for use in children requires careful tailoring of qualitative methods, and performing research within narrow age bands. The best reporter should be carefully considered dependent on the child's age, developmental ability, and the concept being measured, and team completion should be considered alongside self-completion and observer measures.