Principal components regression (PCR) was used to calibrate time-of-flight secondary ion mass spectrometry (ToF-SIMS) positive data against X-ray photoelectron spectroscopy (XPS) data and to predict the relative atomic concentration of the (C-O) functional group on the surface of plasma treated polypropylene films. A multi-component model was constructed and was effective in predicting the relative concentration of surface functional group (C-O) with accurate prediction achieved using an external data set. ToF-SIMS with PCR modelling is demonstrated to provide an alternative method of evaluating the relative atomic concentration of surface functional groups for plasma treated polypropylene films without the need for other quantitative or semi-quantitative techniques such as XPS.