We use Fabry-Perot H \alpha spectroscopy , complemented with published H I 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 \geq 1 .