The increasing interest in area such as pollution control, detection of hazardous gases and monitoring of combustion processes has lent prominence to gas sensing devices. Solid state gas sensors based on tin oxide thin films have become attractive owing to their simplicity and portability. A vast body of literature, including a comprehensive reviews, exists on the formation, defect structure and electrical, and optical properties of SnO2 thin films or nanowires. Especially, for films prepared by CVD or by spraying techniques, the reports on the presence of the Sn (0) and/or Sn(II) phases are quite conflicting. In present study the growth of tin oxide layers on the 1D silicon surfaces has been investigated. The disproportionation of tin dioxide up to metallic tin was observed at 600°C. According to the XRD data we observed, for the first time, during the MOCVD deposition of SnO2 the formation of three different tin phases (SnO2 , SnO and Sn). The ratio between the three phases exhibits a dependence of the length of the nanostructures. The EBSD and PEEM (photo electron emission microscopy, HZB Berlin BESSY II) data confirm the presence of three different phases along the vertical axis of the nanostructures.