3-Dimensionally porous tin oxide (SnO 2 ) foams were fabricated by an electrochemical deposition and their application for gas sensors was investigated. The electrochemical deposition was carried out in an electrolyte containing sulfuric acid and tin sulfate, and Sn film-coated SiO 2 /Si substrate was used as a cathode instead of conventional metal foil, which was deposited by a thermal evaporation. The porous Sn foam structure was formed during electrodeposition and its pore wall was composed of self-supported networked dendrites. The annealing at 700°C converted the Sn foam into the corresponding metal oxide (SnO 2 ) foam with preserving the structural integrity and pore structure. The porous SnO 2 foam sensors responded to H 2 , CO, NH 3 , NO x , and C 2 H 5 OH gases. In particular, the foam sensors showed a significantly higher gas response toward C 2 H 5 OH, and the response time and working temperature were improved due to the rapid gas diffusion through 3D interconnected open porous structure.