Influence of hydrostatic pressure on the light emission from strained GaN/AlGaN multi-quantum-well systems has been studied, Pressure coefficients of the photoluminescence peak energies show a strong reduction with respect to that of the GaN energy ? ap and this reduction is a function of the quantum-well thickness. The decrease of the light emission pressure coefficient may be almost 40% for a 32 monolayer (8 nm) thick quantum well in comparison with a 4 monolayer well. We explain this effect by a hydrostatic-pressure-induced increase of the piezoelectric field in the GaN/AlGaN quantum structures.