Аннотация:We present some our recent results of investigation of singularly perturbed periodic in time reaction-advection-diffusion problems, which are based on a further development of the asymptotic comparison principle. We illustrate our approach for the new problems. The theorems, which states the existence of the periodic solutions with internal layer, gives it's asymptotic approximation and state their Lyapunov stability are proved. We claim that an appropriate combination of asymptotic analysis and numerical schemes should improve the effectiveness of numerical calculations.