We have studied the influence of bond- and site-type impurities on the ground state properties of one-dimensional Peierls systems. Using a functional integral formalism with both commuting and anticommuting variables we have calculated the averaged Green's function which determines the electronic density of states and localization length (Thouless formula). Some limiting cases can be solved analytically. To apply our model to doped polymers we derive the connection between doping concentration and disorder strengths Dj. For illustration we present the results with parameters appropriate for polyacetylene.