We have studied the Raman spectra at different temperatures (74 K < T < 250 K), and oxygen contents (delta = 0 and 0.13) of Ln2NiO4+delta (Ln = La, Pr and Nd) powder samples. The factor group analysis predicts 18 Raman active modes for the stoichiometric samples (delta = 0, orthorhombic D2h18). Nearly all the observed peaks have been identified with concrete atomic displacements even if no selection rules can be applied in powder samples. An electronic transition at 2.06 eV has been observed in the Raman spectra of the La2NiO4 compound that can be associated to the luminiscence in the gap of the material.