A deformation of the Landau problem based on a modification of Fock algebra is considered. Systems with the Hamiltonians f((H) over cap) where (H) over cap is the Landau Hamiltonian in the lowest level are discussed. The case f((H) over cap) = alpha(1)(H) over cap + alpha(2)(H) over cap (2) is studied and it is shown that in this particular example, parameters of the problem can be fixed by using the quadratic Zeeman effect data and the Breit-Rabi formula.