Previous studies on Internet-based treatment with minimal to moderate therapist guidance have shown promising results for a number of specific diagnoses. The aim of this study was to test a new approach to Internet treatment that involves tailoring the treatment according to the patient's unique characteristics and comorbidities. A total of 54 participants, regardless of specific anxiety diagnosis, were included after an in-person, semi-structured diagnostic interview and randomized to a 10 week treatment program or to a control group. Treatment consisted of a number of individually-prescribed modules in conjunction with online therapist guidance. Significant results were found for all dependent measures both immediately following treatment and at 1 and 2 year intervals. Mean between-group effect size including measures of anxiety, depression and quality of life was Cohen's d = 0.69 at post-treatment, while the mean within-group effect size was d = 1.15 at post-treatment and d = 1.13 and d = 1.04 at 1 and 2 year follow-up respectively. The tentative conclusion drawn from these results is that tailoring the Internet-based therapy can be a feasible approach in the treatment of anxiety in a homogeneous population.