Screening of Generalized Anxiety Disorder (GAD), which is often undetected and untreated, could be improved by quick and easy web-based data collection. This paper aims to validate the web-based self-rated 7-item GAD-7, its shortened 2-item GAD-2 and a single item from the GAD-7 scale (GAD-SI) to screen for GAD. Of a total of 502 subjects aged 18-80 who rated the web-based GAD-7, Center for Epidemiological Studies Depression scale (CES-D) and Hospital Anxiety and Depression Scale (HADS), 157 (31%) subjects had a WHO Composite International Diagnostic Interview for DSM-IV-disorders by telephone. The GAD-7 had good reliability. Subjects with a GAD-diagnosis had significantly higher means on GAD-2, GAD-SI and GAD-7 than subjects without a GAD-diagnosis. The AUC (Area Under the Curve) of the GAD-SI and GAD-2 was accurate and not significantly different to the GAD-7 AUC. The web-based GAD-SI, GAD-2 and GAD-7 are reliable, valid tools to quickly screen for GAD in busy mental health settings and clinical research. More research is needed to validate the GAD-SI 'Do you have trouble relaxing' to see if its screening properties approach those of the GAD-7.