  We investigate in detail the mass distribution obtained by means of high
resolution rotation curves of 25 galaxies of different morphological types. The
dark matter contribution to the circular rotation velocity is well-described by
resorting to a dark component whose density shows an inner core, i.e. a central
constant density region. We find a very strong correlation between the core
radius size $R_C$ and the stellar exponential scale length $R_D$: $R_C \simeq
13 (\frac {R_D} {5 {\rm kpc}})^{1.05} {\rm kpc} $, and between $R_C$ and the
galaxy dynamical mass at this distance, $M_{dyn}(R_C)$. These relationships
would not be expected if the core radii were the product of an incorrect
decomposition procedure, or the biased result of wrong or misunderstood
observational data. The very strong correlation between the dark and luminous
scale lengths found here seems to hold also for different Hubble types and
opens new scenarios for the nature of the dark matter in galaxies.
