The base of the operational dependability of a control system is being laid down in the stage of project design. Dependability properties of the whole control system are influenced by dependability properties of components. Functional relations of system components are described by a structural dependability model. The theoretical structural dependability model of an control system was created on the basis of the functional and dependability analyses of an industrial robot control system. The created models were verified by means of operation reliability analysis of chosen real control systems.