This study will primarily investigate whether an individually tailored CBT-treatment administered through the internet can be beneficial for patients suffering from chronic pain and comorbid psychiatric conditions. The project will also clarify whether a following booster-program, also administered tough the internet, is helpful in maintaining and increasing effects of the initial treatment. Lastly, analysis of possible mediating variables will be able to give insight into the internal workings of the treatment itself, further elucidating efficacy of specific interventions, data which will be useful in future developments of treatment design.