The diagnostic performance of the frequency doubling perimetry (FDT) C20-1 screening mode was compared to that of the C20 full-threshold mode. For the number of defects p < 1% in the total deviation plot, both modes appeared to perform similarly in terms of sensitivity, specificity, and area under the receiver-operating characteristic (ROC) curve. Different cut-off points should be applied for both modes to obtain equal sensitivity and specificity values, and - related to that - for most subjects more defects were found in full-threshold mode than in screening mode. For the screening mode, we found a sensitivity of 0.91 and a specificity of 0.88 at a cut-off point of >0 defects, and an area under the ROC curve of 0.93.