We consider a polyharmonic operator H = (-Δ)l + V (x) in dimension two with l > 6, l being an integer, and a limit-periodic potential V (x). We prove that the spectrum of H contains a semiaxis and there is a family of generalized eigenfunctions at every point of this semiaxis with the following properties. First, the eigenfunctions are close to plane waves ei le (k, x) at the high energy region. Second, the isoenergetic curves in the space of momenta vec k corresponding to these eigenfunctions have the form of slightly distorted circles with holes (Cantor type structure). © 2007 Springer Science+Business Media, Inc.