**Victor Fleurov
**

Discrete nonlinear Schroedinger (DNLS) equation is currently a toy model allowing for investigation of dynamics of discrete quantum breathers. This is often done by means of the number representation. Otherwise, DNLS allows for a cannonical transformation, which makes WKB analysis of tunneling between classical isolated periodic orbits (IPO) possible. Considering tunneling between IPO's for general type of systems, which not necesserilly are of a DNLS type, the angle-action representation is used in order to make a WKB analysis possible. It is demonstrated how tunneling amplitude between IPO's in a system of two coupled anharmonic oscillators can be calculated.