No RCT on outcome and effectiveness of classical group CBT for severe health anxiety and hypochondriasis has yet been conducted. Group CBT compared to individual CBT (and usual care) for patients with health anxiety might have some therapeutic advantages due to manualised and structured treatment, favourable group dynamics, improving social skills and creating a support group, group-CBT might be less costly and therefore have better cost-effectiveness, but attrition might be worse, so it needs further investigation.