Chapter 25 discusses the variety of issues that can arise when clients with specific mental and physical health conditions use internet-based CBT programs. A mixture of specific and common challenges are discussed for the mood and anxiety disorders, bulimia nervosa, physical health conditions, and substance use disorders. Issues common to the conditions include maximizing safety (e.g. checking for suicidality), assisting client engagement and maintaining adherence, encouraging self-monitoring, attention to non-specific factors such as therapeutic alliance and hopefulness for improvement, and involving significant others.