ADHD affects executive functions and pharmacological treatment is the most common intervention. Medication is ineffective for some and psychosocial interventions are scarcely available. CBT that teaches organizational skills for managing ADHD-symptoms has shown promising results. Smartphones can help individuals perform executive tasks such as planning and organizationand they could beefficacious as a support tool for ADHD patients. The current study is aRCT that compares an online course (n=29) based on previouslyeffective CBT treatments for ADHD to a wait-list control (n=29). Theintervention focused on teaching the use of an online calendar and smartphone apps. The intervention brought significant improvement (p < 0.001) to participants regarding ADHD symptoms and 38% of participants were considered clinically significantly improved. This indicates that online treatments using IT-tools for ADHD is effective and that smartphones can be used as a tool for aiding individuals with impairments in executive functions.