Abstract This study provides a method of vibration control of large space structures by the simultaneous and integrated structure and control design to reduce structural response from disturbances encountered. The formulation of a design scheme is obtained by structural modification of some nominal finite element model, which is controlled in optimal fashion by a linear regulator, to increase the active modal damping factor beyond that of the nominal structure. The structural modifications are determined by calculating the sensitivity of the closed-loop eigenvalues to structural stiffness variation. Because an optimal active control method is used, the sensitivity of the Riccati matrix to structural modifications are provided. Improvements in modal damping factors are specified and a method for determination of structural modification provided. The structural modifications, i.e. changes in the cross-sectional areas of the members, are achieved by using a nonlinear mathematical optimization technique. Application of the algorithm is illustrated by structural modification of a nominal ACOSS-FOUR model with different constraints on the closed-loop eigenvalues.