We investigate the behavior of the critical temperature Tc in superconductor/ ferromagnet / superconductor (S/F/S) trilayers in the dirty limit as a function of the ferromagnetic layer thickness df and the S/F interface transparency. This system is interesting due to the possibility of realization of competitive 0 and π states. We perform Tc calculations using the general self-consistent multimode approach based on the Usadel equations in Matsubara Green’s functions technique, and compare the results with the single-mode approximation, widely used in the literature. Both methods produce similar results for sufficiently low interface transparency. For transparent interfaces we obtain a qualitatively different Tc(df) behavior [1]. Using the multimode approach we observe multiple 0- π transitions in critical temperature, which cannot be resolved by the single-mode approximation. We also calculate the critical S layer thickness at given df when an S/F/S trilayer still has a nonzero critical temperature. Finally, we establish the limits of applicability of the single-mode approximation.