The Raman spectra of single crystalline RE (rare earth) tetraborides REB4 (RE = Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu) are measured and analysed with respect to the dependence of the phonon frequencies on the rare earth metal. Phonons representing octahedral B6 units are identified by comparison to the according phonon modes of hexaborides. Their relative force parameters are estimated