In this work, X-ray emission lines of the L alpha, L beta, L gamma and Ll groups in elements La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er were studied to examine the influence of 0:6 T and 12 T external magnetic field. The measurements were done using an energy dispersive Si(Li) detector with photon excitation by radioisotopes. A significant dependence of the L X-ray emission lines was observed for Sm but no discernible effect on the Pr La/L gamma intensity ratio was observed. Likewise no significant effect of external magnetic field on the various L alpha/Ll intensity ratios was observed. For B=0, the results are compared with the theoretical data and experimental results in literature. The results demonstrate that the relative intensities are more susceptible to the external magnetic field than the energy shifts. (C) 2013 Elsevier Ltd. All rights reserved.