The paper describes attempts to find advantageous shape and configuration of a manhole located in the upper part of a cylindrical pressure vessel. Manholes of circular and elliptical cross sections have been considered. The manhole is placed vertically and symmetrically with respect to the cylindrical vessel. Three variants of the manhole walls have been taken into account. In the first variant, the manhole wall reaches only the cylinder surface. The manhole walls in two other variants are elongated inside the cylindrical vessel to various lengths. In the case of elliptical manholes two other variants were been considered, i.e. with their major axes situated in parallel or perpendicularly to the axis of symmetry of the cylindrical vessel. Results of the numerical calculation are presented in figures and tables.