Rare-earth-doping and various post-growth heat treatments effects on OH- absorption in singly Er- and Yb-doped, doubly Er/Mg- and Er/Yb-doped LiNbO3 crystals have been investigated. The OH- absorption in the rare-earth-doped crystals shows definite anisotropy and is stronger in a Z-cut plate. Rare-earth-doping causes considerable OH- absorption reduction. MgO-codoping induces additional reduction. Slight/heavy rare-earth-doping causes slight/considerable spectral shape change. Thermal reduction treatment causes OH- absorption vanishing whether the crystal is originally congruent or near-stoichiometric. Further oxidation treatment renders the absorption reemerged. Li-rich vapor transport equilibration (VTE) treatment causes significant absorption decrease. For a slightly rare-earth-doped Li-rich VTE-treated crystal, its spectral feature is similar to that of the undoped near-stoichiometric crystal; for a heavily rare-earth-doped VTE-treated crystal, its spectral shape preserves the feature of the heavily rare-earth-doped as-grown crystal. For the Er/Mg-codoped crystal studied, the Li-rich VTE also induces an abrupt conversion of peaking position from 3483 cm(-1) to 3535 cm(-1). The absorption in the Li-rich WE-treated crystals also reveals aging effects in spectral shape, peaking position and absorption intensity. Li-poor VTE induces significant absorption increase. In addition, the effect of OH- presence on lifetime of Er3+ emission at 1.5 mu m was also studied. The results show that the effect is small for the as-grown congruent crystals and slight for Li-rich VIE-treated ones. (C) 2012 Elsevier B.V. All rights reserved.