  We present here simultaneous INTEGRAL/RXTE observations of Sco X-1, and in
particular a study of the hard X-ray emission of the source and its correlation
with the position in the Z-track of the X-ray color-color diagram. We find that
the hard X-ray (above about 30 keV) emission of Sco X-1 is dominated by a
power-law component with a photon index of ~3. The flux in the power-law
component slightly decreases when the source moves in the color-color diagram
in the sense of increasing inferred mass accretion rate from the horizontal
branch to the normal branch/flaring branch vertex. It becomes not significantly
detectable in the flaring branch, where its flux has decreased by about an
order of magnitude. These results present close analogies to the behavior of GX
17+2, one of so-called Sco-like Z sources. Finally, the hard power law in the
spectrum of Sco X-1 does not show any evidence of a high energy cutoff up to
100 - 200 keV, strongly suggesting a non-thermal origin of this component.
