A continuously or/and discontinuously tunable LiNbO 3 Optical Parametric Oscillator (OPO) with the spectral range of 1.42 -4.24 um and shifting of 0…12 nm is created and investigated. The OPO resonator ring circuit provides for the radiation energy output value of up to 50 mJ. Radiation bandwidth narrowing of up to 0.7 cm -1 by introducing of the Fabry-Perot etalon into the OPO resonator has been obtained.