We present the results of a study of some selected spectral regions, including those around the LiI lines at 6708 Å and 6104 Å in the magnetic chemically peculiar star HD 3980 and in a few other Ap stars with different effective temperatures and different strengths of the magnetic field. High resolution spectroscopic observations were carried out with the Coudé echelle spectrograph at the 74-inch telescope of the Mount Stromlo Observatory ($R=88000$) and with the VLT UV-Visual Echelle Spectrograph UVES at UT2 at ESO ($R=110000$). Using spectral synthesis we determined abundances of Li, Ce, Pr, Nd and some other rare earth elements and showed that the spectral feature at 6708 Å in the spectrum of HD 3980 is due to the Li I doublet with only a minor contribution of the Ce II line at 6708.099 Å.