Ground state spontaneous magnetization study for the Y-2(Fe1-xCox)(14)B and Y2Fe14BHy intermetallic compounds in magnetic fields up to 140 kOe have been performed. Obtained results can be summarized as following: the 3d-ion subsystem magnetization (M-d) does not increase upon the substitution of Co for Fe even for a small Co content, which is unusual for the CoxFe1-x alloys or other similar intermetallic compounds, but agrees well with the 3d-band structure for Y2Fe14B, if the density of states picture for the spin-up and spin-down subbands is not changed upon such substitutions (rigid band model). In Y2Fe14BHy the M-d increases with the hydrogen content increase. This can be explained by the fact that in the Fe-containing compounds, hydrogen atoms produce low-energy electron states. Leaving the 3d-band 3d electrons transit to these states. This is accompanied by the Fermi level displacement to the "left'' and increase in the 3d-band splitting, resulting in the M-d rise. (C) 2005 Elsevier B.V. All rights reserved.