In the present paper, some problems of the "surface resolution analysis" to characterize silica gels are addressed. We measured the adsorption of organic adsorbates (fatty acids, aliphatic alcohols, and ketones) from CCl4 solution on mesoporous silicas of various porosity. A simple linear relationship is found between the monolayer thickness and the monolayer volume, which is valid even for the adsorbates of different homology series. A simple model to describe adsorption experiments quantitatively has been developed. The model shows that the curvature of silica mesopores may influence the packing of test molecules in the monolayer, and leads to a decrease in the adsorbate monolayer capacity for large molecules, so that measured surface area is underestimated. The effect increases when the ratio of adsorbed layer thickness h to pore radius R increases and may reach some tens of percent. The model explains why the apparent values of silica surface dimension may be abnormally high (D-s > 3).