We present a circuit model and parameter determination methodology for test fixtures used for on-wafer S-parameter measurements on CMOS devices. The model incorporates the frequency dependence of the series resistances and inductances due to the skin effect occurring in the metal pads. Physically based representations for this effect allow for excellent theory-experiment correlations for different dummy structures, as well as when de-embedding transistor measurements up to 60 GHz. VC 2012 Wiley Periodicals, Inc. IntJ RF and Microwave CAE 23:655–661, 2013.