Background: Although cognitive behavioural therapy (CBT) has been shown to be an efficacious treatment for social phobia (SP), many patients drop out or achieve little or no benefit from treatment. This fact is generally considered an argument for the importance of studies of predictor variables. Aims: This paper systematically reviews pre-treatment patient variables as predictors of drop-out from and outcome of CBT for SP. Method: A structured literature search was conducted in PsycINFO, Embase and PubMed. Results: 28 published studies with n>or=60 were located. No pre-treatment patient variables were found to predict drop-out. Consistently across studies, higher levels of pre-treatment symptomatic severity predicted higher levels of end-state symptomatic severity, but not degree of improvement. There was some evidence that comorbid depression and avoidant personality disorder before treatment negatively influenced post-treatment end-state functioning, but not consistently improvement. No other patient variables consistently predicted outcome across studies. Conclusions: Generally, the results are in line with the conclusion that more disturbed patients with SP both begin and end treatment at a higher symptomatic level but with a similar degree of improvement. There is, however, little clinically or theoretically relevant knowledge to be gained from existing studies of pre-treatment patient variables as predictors of drop-out and treatment outcome in CBT for patients with SP. The field is in need of conceptual and methodological improvements if more solid findings should be hoped for.