Abstract: Online health forums are an important avenue for receiving social support and learning about fellow patients' experiences with similar diagnoses. We seek to understand what kinds of external information (i.e., web links) are shared on online health forums as a proxy to participants' information needs. For this purpose, we collect a dataset of web links shared publicly on a lung cancer forum over a period of 16 years and perform a comparative analysis with three different website typologies, uncovering a diverse ecosystem of websites. To understand changes in the role health forums play for patients, our study also investigates typological variations as this forum gains and then loses popularity over time.