Most biological soft tissues exhibit viscous behavior in addition to their well known elastic properties. Polyacrylamide gel based tissue mimicking phantoms have been developed. The viscoelastic properties of these phantoms were measured by subjecting the samples to cyclic loading. Samples prepared with varying concentration of monomer were considered so as to cover the normal and pathological lesions. Results obtained in the measurement are fit to three models - Maxwell, Kelvin-Voigt (KV) and Kelvin-Voigt Fractional derivative (KVFD) models, in order to determine the best fitting model. KVFD model is found to be best fitting model for the experimental data obtained. © 2009 IEEE.