Inclusion Criteria:  Patients over 16 years of age Living in Sweden Primary diagnosis of hypochondriasis according to ICD-10 Able to read and write Have access to a computer or other device with an Internet connection If on medication, have a stable dose of psychotropic medication for 4 weeks prior to treatment Not having other psychiatric difficulties (e.g., ongoing substance abuse or a psychotic syndrome) that makes ICBT an unsuitable intervention  Exclusion Criteria:  Patients with severe depression (clinician rated Montgomery-Asberg Depression Rating Scale- Self-Rated; MADRS-S and/or moderate to high risk of suicide in which monitoring is required Patients with low motivation, severe apathy, or difficulty concentrating Patients with psychosis Patients with untreated drug or alcohol problems Patients with reading and/or writing difficulties, including language difficulties;