The compounds synthesized in the ternary systems  La-TM-B, Gd-TM-B et Y-TM-B (TM=Ni, Fe, Co) were studied in terms of their crystal structure, chemical composition and hydrogen sorption properties. Most of the compounds obtained in these systems crystallize with a CeCo₄B type structure, with lattice parameters close to those of the compound GdNi₄B. A total replacement of Ni by Fe and/or Co is sometimes possible, meaning that a total solid solution exists between RENi₄B and REFe₄B or RECo₄B. Also, the boron is assumed to partially occupy two different crystallographic sites, although only one of these is mainly occupied by boron. The new phase GdNi_2.5B_2.5 was also observed in this study for the first time. In addition, a pseudo-binary phase GdB₃ is observed. Finally, it is reported that only the compound LaNi₄B absorbs hydrogen, albeit irreversibly.