Panic disorder with or without agoraphobia (PD/A) is a disabling disorder that involves physical anxiety symptoms, maladaptive cognitions and avoidance behaviour. Internet-based cognitive behavioural therapy (ICBT) can provide accessible mental health care to those who suffer from PD/A, which may increase the uptake of psychological treatment. The literature on ICBT for PD/A shows largely positive results, especially for therapist-guided ICBT among the general population. Unguided ICBT for PD/A is less studied. It has also demonstrated positive results, but is commonly associated with higher attrition than guided ICBT. There is also some evidence that guided ICBT for PD/A is effective for inpatients. Cost-effectiveness of ICBT for PD/A has only been minimally studied, but some evidence indicates it can be cost saving compared with face-to-face CBT. This chapter further describes the existing ICBT programmes for PD/A, a case study and implementation examples from Sweden and Australia. Finally, this chapter discusses the feasibility of minimally guided ICBT and current innovations in ICBT for PD/A, such as the use of mobile technology and virtual reality, and provides future directions for research and development.