True amplitude seismic migration is the procedure, which provides not only the localization of geological objects but also the restoration of their so-called "reflectivity". This characteristic gives very important quantitative additional information about elastic parameters of the objects of interest. The paper addresses 3D seismic depth true-amplitude migration of 3D irregular data in anisotropic media based on beam decomposition of the data. The main objective is the development of the imaging procedure suitable for anisotropic media and handling 3D irregular seismic data without any preliminary regularization. The key components providing the desired image are elastic anisotropic Gaussian beams. Depending on the choice of the beam (quasi P or quasi S) we have PP-or PS-images. Results of synthetic and real data processing are presented and discussed.