In this study, sulfur poisoning behavior is investigated on a 5 × 5 cm 2 anodesupported cell as a function of H 2 S concentration, cell voltage, and in-plane region. At a lower cell voltage, the 1st drop % in the current density decreases by promoting sulfur desorption while the 2nd drop % increases slightly. The outlet regions with poor performance show a lower drop % owing to the water vapor effect, while the inlet regions with superior performance show a higher drop %, especially at high H 2 S concentrations. Ni oxidation in the inlet regions is caused by the substantial 2nd drop under the combined conditions of high current density and H 2 S concentration, whereas that in the outlet region is caused by the high H 2 O concentration. The results indicate that in-plane performance variation may aggravate sulfur poisoning in the inlet regions, whereas it may lead to Ni oxidation in the outlet regions.