Stability and dissolution of platinum single-crystal surfaces were investigated with atomic force microscopy and inductively coupled plasma mass spectrometry. Both low-index surfaces and nanofaceted surfaces were investigated. A clear difference was observed between the large low-index surfaces and the nanofaceted surfaces. In the low-index surfaces, the platinum oxide formation passivates the surfaces, resulting in a lower dissolution rates at higher potentials. The nanofaceted surface dissolves faster at a higher potential, indicating the edges and corners are the main sources of dissolution. The differences in the dissolution behaviors between the low-index surfaces, (111), (100), and (110), are also discussed.