Multiwall (MWNT) and single wall (SWNT) carbon nanotubes were intercalated with heavy alkali metals. From the point of view of their composition, alkali 2D superlattice, EPR and C-13 NMR characteristics, the intercalation compounds of MWNT (1(st) and 2(nd) stage) are close to their parent GIG. An expansion of the 2D triangular lattice of SWNT bundles was clearly detected, showing that the alkali atoms are intercalated in the free space between the tubes.