Mental disorders are a recognized population health issue, with recent estimates placing mental illness as the first in global burden of disease in terms of years lived with disability, and comparable to cardiovascular and circulatory diseases in terms of disability-adjusted life years. Common mental disorders refer to a range of anxiety and depressive disorders, which are prevalent disorders around the world (4.4% and 3.6% of the global population suffer from depression and anxiety disorders, respectively), with variations across different regions and populations [1]. Despite the human, social, and economic costs of mental disorders, mental health has been often neglected. Recently, the Lancet Commission on Global Mental Health and Sustainable Development launched a report recommending that mental health should be reframed as a fundamental human right, and that the definition of mental health should be expanded to promote mental wellbeing, prevent mental health problems, and enable recovery from mental disorders.Despite this, we still face great inequalities in access to mental health promotion, prevention, and treatment programs worldwide (e.g., limited resources to accommodate the existent needs) and/or treatment uptake barriers, such as attitudinal barriers (e.g., stigma towards mental health) or structural barriers (e.g., geographical or financial restrictions, work constraints, or patient's physical conditions). The delivery of psychological services-including assessment/monitoring, mental health promotion, prevention, and treatment-through information and communication technologies (ICT) may be an effective way of improving individual access and use of mental healthcare services [2]. ICT-delivered psychological services include (but are not restricted to) web-based interventions, mobile apps, videoconferencing systems (telepsychology), or virtual reality systems, and may be used complementary to face-to-face services or as the sole means of access to psychological interventions. The use of ICT-delivered psychological services has several advantages, related with increased accessibility and flexibility, self-monitoring integrated into treatment, and empowerment promotion, as well as increased novelty and appeal. However, we cannot exclude that they also have challenges and limitations, related with low digital literacy or with safety and privacy issues, among others [2].The present Special Issue focuses on acceptability, cost-effectiveness, potentialities, and limitations of ICT-based psychological services for mental health promotion, prevention, and treatment. Sixteen articles are included in this special issue from different international research teams working in China, Portugal, Spain, and the United States.Five of the studies included in this Special Issue focused on the assessment of ICT tools for the prevention [3,4] and treatment [5,6] of mental disorders, or the promotion of mental health [7], in different populations. Specifically, these studies examined the interventions' effectiveness, clinical...