  We used a diffusion Monte Carlo technique to describe the properties of
fully-heavy compact arrangements (no dibaryon molecules) including six quarks
and no antiquarks within the framewok of a constituent quark model. Only
arrangements whose wavefunctions were eigenvectors of $L^2$ with eigenvalue
$\ell$ = 0 were taken into account, what means that we only considered the
subset of all the possible color-spin combinations that make the total
wavefunctions antisymmetric with respect to the interchange of any two quarks
of the same type. This means arrangements with spin $S=0$ for $cccccc$,
$bbbbbb$, $cccccb$, $bbbbbc$ and $cccbbb$ and spin $S=0,1,2$ for the $ccccbb$
and $bbbbcc$ hexaquarks. In all cases, the masses of the six-quark arrangements
are larger that the ones corresponding to the sum of any of the two baryons we
can split them into, but smaller that the ones for a set of six isolated
quarks, i.e., all them are bound systems. The analysis of their structure
indicates that all the hexaquarks considered in this work are compact objects,
except the $cccbbb$, that appears to be a loose association of two baryons.
