The problem of independence and completeness of rotation moment invariants is addressed in this paper. General method for constructing invariants of arbitrary orders by means of complex moments is described. It is shown that for any set of invariants there exists relatively small basis by means of which all other invariants can be generated. The method how to construct such a basis is presented. Moreover, it is proved that all moments involved can be recovered from this basis. The basis of the 3rd order moment invariants is constructed explicitly and its relationship to Hu’s invariants is studied. Based on this study, Hu’s invariants are shown to be dependent and incomplete.