Resorcinol-formaldehyde resin (RFR) was synthesized as a porous material characterized by specific surface area of 140 m 2 /g and pore volume of 0.59 cm 3 /g with major proportions of broad mesopores and macropores. The interfacial behavior of water at low (h = 0.05 g of water/gram of dry RFR) and high (h = 2 g/g) hydration degrees depends on temperature and pore size filled by unfrozen water because its freezing-point depression increases in narrower pores. When water is mixed with co-adsorbates, the effects of such co-adsorbates as non-polar, weakly polar and polar organics depend on the amounts and the pore sizes. Even at a low hydration degree (h = 0.05 g/g), a portion of water can be displaced from pores by organic co-adsorbates because water has a relatively weak interaction with the RFR surface.