A semi-analytical higher-order isoparametric finite element is applied to moderately thick composite laminated shells of revolution to study the effect of coupling due to the symmetric modes on vibration characteristics. An improved shell theory with shear deformation and rotatory inertia is used for the investigation of vibration behavior of cylindrical shells. Comparison of natural frequencies of shells using thin- (Love's first-approximation shell theory without thickness normal strain and rotatory inertia) and thick-shell theories is made. The effect of thickness variation along the axial direction with a constraint on total mass is also studied. To check the computational implementation the present results are compared with published values. © 1992.