Discoid red blood cells (RBCs) deposited irreversibly on a horizontal glass surface are studied by means of optical microscopy and image analysis. The relative surface covered by the RBCs, as well as the variance of this surface coverage as a function of the cell concentration, are analyzed and compared to the results derived from the ballistic deposition (BD) model. This model describes the irreversible deposition of spherical particles under the influence of an infinitely large gravitation force and does not allow for overlaps between adsorbed particles. In spite of these characteristics, the BD model permits, surprisingly, to reproduce our experimental observations on the deposition of RBCs on a flat surface. This finding is discussed, in particular in respect to a former study where a model was developed for colloidal particles of this particular geometric shape.