This article presents the results of a comparative study on the modification of the surface layer of carbon composites. Fibre-reinforced polymer (FRP) composite materials are heterogeneous and anisotropic materials, characterised by high strength, low density, corrosion resistance along with ease of processing and moulding, and are increasingly replacing metal alloys. They are widely used in aviation, automotive and transport applications. One example of a modern composite is carbon fibre-reinforced polymer (CFRP). This study presents the influence of selected modifications of the surface layer of a CFRP composite on the values of free surface energy (SFE) and surface topography. The resulting SFE values were analysed together with the contribution of the polar SFE and dispersive SFE components. The article also presents the test results related to selected 3D surface roughness parameters and includes photographs of the test specimens after surface layer modification. The results were statistically processed in compliance with good research practice.