The present paper is primarily devoted to the study of the vibrations of a cylindrical shell with a panel or a flange of a circular plate in the intermediate section. Frequencies and displacements are determined by means of minimizing the total Lagrangian. The numerical calculations are restricted to the cylindrical shell having both ends built-in and three displacement waves along the circumference. Frequencies, displacements and bending moments are shown in the figures. In a certain narrow range of frequency, the magnitude of displacement of vibrating circular plate becomes large almost independently of the length of the shell and the position of the panel, while that of the cylindrical shell gets very small. Except the above case, in general, vibrations of a cylindrical shell of the same dimension freely supported or clamped in the same section with the panel, and then the displacement of the panel is small compared with that of the cylindrical shell.