In this work computer modelling investigations are reported into the chemical functional groups that are believed to contribute to composite fibre/matrix adhesion. The CERIUS [Compos A: Appl Sci Manuf 29 (1998) 1291] and MOPAC computational packages are employed to simulate the sorption interactions of small molecules at a range of functionalised surfaces. The results of these calculations are compared with fibre surface energetic data reported previously, and models of the fibre surface chemistry with varying degrees of surface treatment are developed. There is agreement that surface treatment of carbon fibres improves adhesion and adsorption characteristics, yet the factors controlling this have still to be determined fully. The empirical study using the computational model developed in this work attempts to resolve the changes in fibre adsorption phenomena into contributions arising from specific surface oxygen and nitrogen functional groups. The general trend in surface concentration of these atoms is similar to XPS analyses of the surface treated carbon fibres and is in agreement with previously published work.