  We use Fabry-Perot Halpha spectroscopy, complemented with published HI radio
synthesis observations to derive high resolution rotation curves of spiral
galaxies. We investigate precisely their inner mass distribution and compare it
to CDM simulations predictions. Having verified the existence of the so-called
core-cusp problem, we find that the dark halo density inner slope is related to
the galaxy masses. Dwarf galaxies with V_max < 100 km/s have halo density inner
slope 0 < \gamma < 0.7 while galaxies with V_max > 100 km/s are best fitted by
\gamma >= 1.
