The purpose of this article is to describe an internet-based platform for improving symptoms and quality of life for people with psychological and behavioural health problems such as depression, anxiety, phobia, psychological trauma, hearing loss and tinnitus. The online platform, called Iterapi, was developed at the Department of Behavioural Sciences and Learning at Linköping University, Sweden and has been running for nearly two decades and used in many randomized controlled trials and outpatient treatments.The intention of this article is to share our experience with developing such a treatment solution and the process flow and elements of running internet-based psychological interventions. This will likely be of use to developers building similar services, therapists considering integrating such approaches in their practices and institutions, as well as researchers curious about the functions included on the platform and methodology used for running studies.We describe the security aspects of the platform, central concepts underlying its development, how the platform can be used in a study or treatment and the main features and functions the platform offers. We comment on practical considerations regarding blending of methods within the platform, such as self-help treatments with asynchronous communication and real-time text chat and video conversations. We also point out the advantages of using Internet-assisted treatments, the challenges that we have faced and future planned upgrades.Due to continuous development of the platform, its user-friendliness, accessibility across devices and numerous features, many research colleagues from Sweden as well as other countries such as Germany, United Kingdom, Romania and Israel have chosen to implement their own studies on the platform.