We consider a problem of an optimal control in coefficients for the system of two coupled elliptic equations also known as thermistor problem which provides a simultaneous description of the electric field u = u(x) and temperature θ(x). The coefficients of operator div (A(x) ∇ θ(x)) are used as the controls in L ∞ (Ω). The optimal control problem is to minimize the discrepancy between a given distribution θ d ∈ L r (Ω) and the temperature of thermistor θ ∈ W 1,γ 0 (Ω) by choosing an appropriate anisotropic heat conductivity matrix B. Basing on the perturbation theory of extremal problems and the concept of fictitious controls, we propose an "approximation approach" and discuss the existence of the so-called quasi-optimal and optimal solutions to the given problem.