Attention deficit hyperactivity disorder is a disorder characterized by, hyperactivity, impulsivity, lack of attention.The condition results in several impairments that can impair everyday functioning and lead to underperformance. At present, there are not many large scale studies that have investigated the effect of Internet-based Cognitive Behavioral Therapy (iCBT) for ADHD symptoms. This study presents the outcome of a clinical trial of internet- based cognitive behavioral therapy (iCBT), using a randomized controlled study design, with the primary aim to increase quality of life, as well as to reduce symptoms of ADHD, anxiety, depression, and stress. Approximately a hundred participants with symptoms of ADHD will be included in the first wave (recruitment for the second wave comprised of an additional 100 participants is ongoing) and randomized to two conditions (treatment and wait-list control). The treatment period is comprised of ten weeks, with two mandatory modules and ten modules from which the participants can choose freely. The study utilizes an intention to treat design, with ANOVAs and Reliable Change Index to evaluate treatment effects both on an individual and group level. Implications for iCBT for ADHD symptoms will be discussed.