A new test structure for the recombination lifetime profile measurement has been designed and applied, for the first time, to characterize very thin(4 mu m) silicon epitaxial layers, The results of our analysis have shown how the lifetime behavior, at room temperature, is clearly position dependent its value being influenced by different recombination centers, Moreover, two distinct recombination centers have been identified, the first one related to the dopant (arsenic in our case) and the second one induced by the process steps required to realize the test structure itself.