The atomic force microscope is broadly used to study the morphology of cells^1–5 but it can also probe the mechanics of cells. It is now known that cancerous cells may have different mechanical properties than normal cells^6–8 but the reasons for these differences are poorly understood⁹. Here we report quantitatively the differences between normal and cancerous human cervical epithelial cells by considering the brush layer on the cell surface. These brush layers, which consist mostly of microvilli, microridges, and cilia are important for interacting with the environment. Deformation force curves obtained from cells in vitro are processed according to the ‘brush on soft cell model ¹⁰. We found that normal cells have brushes with one length while cancerous cells displayed long and short brushes with significantly different densities. The observed differences suggest that brush layers should be taken into account when characterizing the cell surface by mechanical means.