The bright low-mass X-ray binary Cyg X-2 was in the field of view of the IBIS telescope during the early Cygnus region observations , executed during the INTEGRAL Performance Verification Phase .
The data presented are spanning about one week and cover the rising edge of one of the two peaks of the \approx 82 day cycle of the Cyg X-2 light curve .
The IBIS data in the energy range 20-40 keV exhibit flux variation correlated with the RXTE /ASM light curve .
Two different main exposures , separated by \approx 5 days are found to be characterized by sensibly different spectra , with significant softening and higher X-ray luminosity in the second part , coincident with the long-term cycle peak .
At high energies , both measured spectra are very steep .
The ratio of the 30-45 keV and 20-30 keV detected fluxes is \approx 0.30 , against a value of 0.95 expected for a Crab-like spectrum .
No positive detection exists for E \geq 45 keV , with a flux upper limit ( 5 \sigma ) of \sim 1.4 \times 10 ^ { -10 } erg cm ^ { -2 } s ^ { -1 } 
in the 45-100 keV band .