The aim of this study is to better understand the heterogeneity and microstructural properties of the skin of concrete. The microstructural evaluation of the skin of concrete was performed using X-ray micro computed tomography (micro-CT). The concrete surface was treated using four methods, due to which different surfaces were obtained, i.e. a raw surface, a surface formed after contact with formwork, a grinded surface and also a shotblasted surface. The results of the pore structure obtained from the micro-CT images were used to assess the influence of selected surface treatment method on the nature of the skin of concrete. It was shown that the thickness and unique nature of the skin of concrete differ for various surface treatment methods. (c) 2017 Elsevier B.V. All rights reserved.