The reduced charge montmorillonite (RCM) samples were prepared by heating the exchanged formof lithium at different temperatures for 24 hours. Calcium exchanged forms were used for the study of the interaction with water. The collapse of the interlayer spaces lowered the accessible surface area for the water molecules and decreased the water sorption. Induced acid treatment (after lithium reaction with hydroxyl groups) caused the dissolution of the structure and enhanced specific surface area. The samples with reduced layer charge, but without collapsed interlayers exhibited the highest affinity to water.