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.
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