The given work to some extent meets the shortage of experimental investigations directed to the study of the behavior of buildings with dynamic oscillation dampers. Investigations were carried out by means of vibration testing on a large-scale model of a 9-story frame building. The purpose was revealing the effectiveness and damping properties of two-mass damper and comparing them with the effectiveness of single-mass damper. Before construction of such a damper in a form of an additional tenth floor, the dynamic characteristics of the model (periods and damping factors) were determined and their values are given in the paper. It was revealed that the maximum amplitude of oscillations on the top level of model (the slab of the 9th floor) with the main damper is almost 3 times less than the amplitude of oscillations on the top level of the model without damper. The amplitude of oscillations of the main damper was about 3-4 times bigger than the amplitude of oscillations on the top level of model. A damping factor of the main damper determined by the record of free oscillations was equal to ξ=0.7%. Then the damper was transformed from the single-mass to the two-mass damper by suspending the second mass to the slab of the main damper The obtained results show the high effectiveness of the two-mass damper as its damping degree reaches to about 4.4, that is 46.7% bigger than that of onemass damper. If before suspending the second mass to the single-mass damper its maximal amplitude was about 3.5cm, then after it the amplitude became equal to 1.4cm. The experimental investigations confirm the quite high effectiveness of the dynamic oscillation dampers and incontrovertible expediency of their application for increasing of earthquake resistance of buildings and structures.