In this paper the dielectric spectra of blood serum of chronic lymphocytic leukemia patients and healthy donors were revealed at room temperature in the frequency range f = 106 – 109 Hz. The relaxation parameters of the systems under study were estimated in the Havriliak-Negami approximation for the electric modulus. The decrease of the electrical conductivity for patients is associated with a decrease in the concentration of free charge ions. It may be due to that for patients the conformation of proteins change, which increase their dipole moment and leads to the formation of protein clusters. Some of free ions are solvated around these clusters