The paper presents the results of a systematic comparative study of the two most frequently used dynamic models of earth dams: the plane-strain and the shear-beam models. Five different earth dam cross-sections are considered, all having the same height (90 m) and the same average S-wave velocity (324 m/s); two uniform dams having up- and down-stream slopes 2.5 : 1 and 2.0 : 1, with and without water seepage, respectively; two dams with slopes also 2.5 : 1 and 2.0 : 1 having a central core characterized by two different stiffnesses and one uniform dam with both slopes equal to 1.5 : 1. In all dams soil moduli are distributed in proportion to the square-root of the (local) effective confining pressure and a finite-element formulation is utilized for the plane-strain analyses. The implemented shear-beam model is based on a variation of modulus with depth-from-the-crest compatible with the above distribution of moduli. By comparing the natural periods and the modal displacement shapes of the five dams considerable insight is gained into the nature of the free vibration characteristics of earthfill dams and conclusions are drawn regarding the applicability of the ‘generalized’ shear beam model to assess their dynamic behavior.