We report the studies on the frequency dependence of the complex permittivity (epsilon* = epsilon＇ - i.epsilon ") and of the electromagnetic interference shielding (EMI) of the conducting polymers such as poly(para-phenylene-vinylene) (PPV) and poly(2,5-dimethoxy,1,4-phenylene-vinylene) (DMeO-PPV) doped with different dopants. Permittivity measurements from 10 kHz to 10 GHz point out that all conducting polymers doped with H2SO4 show a conductivity range of 10(-1)-10(+1) S cm(-1), but doped DMeO-PPV has conductivity slightly higher than that of PPV. From these experimental data, the reflectivity coefficients of these materials are calculated in a frequency range 3-5 GHz, and have the values up to -30 dB depending on the frequency, on the thickness of the materials, on the dopant agents and specially on the doping levels of the materials. The potential applications of these materials in EMI shielding are discussed.