In this article, we examine the opportunities and constraints of professionally mediated social networking in health promotion practice. Our analysis is based on the findings of a 12-week participatory study of a peer-led support intervention for youth with asthma and life-threatening allergies. The article begins with an overview of the preferences of youth, their parents, and young adults recruited as peer mentors for online features in the design of a customized support program. We then briefly explain the rationale behind our decision to design and host our intervention using a publicly available website called Ability Online in an effort to balance participants’ preferences with important research obligations and safety requirements. Finally, we report on participants’ level of satisfaction with the intervention as well as recommendations for health practitioners who wish to use social networking to enhance supports for youth with chronic health conditions.