A comparative study of the infrared spectra of Nd2Cu1-xAgxO4 and La1.8Sr0.2Cu1-xAgxO4 is reported. It is shown that the appearance of an absorption peak at similar to 680 cm(-1) is due to local distortions around the Ag impurities, and the appearance of this peak need not imply a structural transformation from Nd2CuO4 type of K2NiF4 type. It is shown that Nd2CuO4 structure is not important for the superconductivity of La-Sr-Cu-O system.