Mental illness has been identified as one of the greatest challenges facing society in the coming decades. However, there are significant barriers to access for many people suffering from mental illness, including overburdened public health care systems, geographic distance from point of care, difficulties encountered by individuals in engaging with services, and the stigma associated with mental illness. Technology has the potential to significantly improve access, engagement, effectiveness and affordability of treatment, yet relatively little use has been made of technology to date. Significant opportunities exist for further research and development, but the domain throws up a variety of challenges for HCI design and HCI methods. Keywords Mental health, psychotherapy, cognitive rehabilitation, computer based treatment, exposure therapy, stigma, engagement, universal design, ethics, user centered design. ACM Classification Keywords H.5.2. User interfaces (User-centered design, evalu...