We report a modification in the etching characteristics of lithium niobate (LiNbO3) single crystals induced by irradiating the crystal surface with pulsed UV laser light at fluences just below the ablation threshold. Modified etching behaviour has been observed using 248, 308 and 355 nm light from excimers and frequency tripled YAG lasers, for x-cut and z-cut surfaces. Both etch enhancement and etch frustration has been observed, depending on the choice of irradiation conditions. The maximum depth of surface relief structures achieved so far is > 2 μm for the -z face, using etching frustration. The potential applications for microstructuring LiNbO3 using these modified etching techniques are also discussed.