  Magnetic susceptibility $\chi$ of pristine and brominated arc-produced sample
of multiwall carbon nanotubes was measured from 4.2 to 400 K. An additional
contribution $\Delta \chi(T)$ to diamagnetic susceptibility $\chi(T)$ of carbon
nanotubes was found at T $<$ 50 K for both samples. It is shown that $\Delta
\chi(T)$ are dominated by quantum correction to $\chi$ for interaction
electrons (interaction effects-IE). The IE shows a crossover from
two-dimensional to three-dimensional at $B$ = 5.5 T. The effective interaction
between electrons for interior layers of nanotubes are repulsion and the
electron-electron interaction $\lambda$$_c$ was estimated to be $\lambda_c\sim
$ 0.26.
