  We present and discuss new result from mm-VLBI observations of M87 and SgrA*,
using the Global mm-VLBI array (GMVA). New 3mm-VLBI images of the inner jet of
M87 are presented, showing details with a spatial resolution down to 15
Schwarzschild radii. This resolution corresponds to a similar spatial
resolution (in terms of R_s) obtained for Sgr A*. We discuss existing and new
size determinations for this source provided by mm-VLBI at wavelengths of 3, 2,
and 1.4 mm. With respect to the morphological difference between Sgr A* and M87
(the latter exhibits a long jet), a comparison of the sub-milliarcsecond
structures seen with mm-VLBI may lead to a better understanding of the
astro-physical processes acting in the vicinity of super-massive black holes.
