Three problems in the theory of adsorption of a polymeric chain are discussed in the present paper. It is shown that the phase transition during the adsorption of a macromolecule without volume effects should be treated as the passage through a tricrital point along the lines of the phase transition. Adsorption of a chain on to the surface of a cylinder of radius R is discussed. It is shown that, as R increases, the temperature of adsorption always reaches a value characteristic of adsorption on to a plane before the step increase in heat capacity occurs. The limits of applicability of the ideal chain model for adsorption on to a plane, line and point have been analysed. It is shown that, in the case of adsorption on to a surface or line, volumetric effects exist under the same conditions as in a free coil.