The structure of water in perfluoropolyether (PFPE) ammonium salt/water systems and in PFPE surfactant/PFPE oil/water ternary systems has been studied as a function of the water/PFPE ratio (W) by using the absorption IR due to O-D stretching modes in the 2800-2000 cm(-1) frequency range. The results show that the LR spectra can be expressed as the sum of contributions from interfacial and bulklike water. The relative amounts were evaluated as a function of W in the 3.8-102 range. The data show that a pool of bulklike water develops in these systems as the water amount increases and suggest the simultaneous presence of two water regions with different structural and dynamical properties.