The　membrane　electrode　assembly　(MEA)　of　a　proton　exchange　membrane　fuel　cell　(PEMFC)　would　deform　when　there　is　a　pressure　difference　between　the　cathode　and　anode.　In　this　study,　a　three-dimensional　PEMFC　model　that　incorporates　a　twodimensional　MEA　deformation　model　is　employed　to　investigate　the　effects　of　the　curved　MEA　on　oxygen　transport,　liquid　water　removal,　pressure　drops　across　cells,　and　resulting　overall　cell　performances.　The　results　show　that　the　MEA　deformation　generates　a　gap　between　the　rib　and　gas　diffusion　layer　(GDL),　thereby　enhancing　the　oxygen　transport　into　and　liquid　water　removal　from　the　cathode　porous　electrode.　At　an　operating　voltage　of　0.4　V,　the　output　current　density　is　enhanced　by　4.83%,　6.67%,　and　8.61%,　respectively,　for　the　pressure　differences　of　10,　20,　and　30　kPa　between　the　cathode　and　anode,　as　compared　with　that　without　a　pressure　difference.　An　efficiency　evaluation　criterion　(EEC)　that　represents　a　tradeoff　between　mass　transfer　enhancement　and　pressure　drop　penalty　is　introduced　to　evaluate　the　overall　cell　performance　enhancement.　The　result　shows　that　the　EEC　value　increases　with　increasing　the　pressure　difference　between　the　cathode　and　anode,　confirming　the　performance　enhancement　by　the　deformed　MEA.　In　addition,　the　effects　of　MEA　deformation　are　also　examined　at　two　sets　of　channel　heights　(H)　and　widths　(W),　i.e.,　W=H=0.5　mm　and　W=H=1.5　mm.　At　an　operating　voltage　of　0.4　V,　the　output　current　density　is　enhanced　by　20.18%　at　a　pressure　difference　of　30　kPa　for　the　cell　with　W=H=0.5　mm,　whereas　it　is　improved　only　by　2.91%　for　the　cell　with　W=H=1.5　mm.　Therefore,　increasing　the　pressure　difference　between　the　cathode　and　anode　is　a　more　effective　approach　to　performance　enhancement　for　the　cell　with　a　small　channel　height　and　width.　(c)　2021　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.