This paper presents the analysis of C and X band images in the scope of soil moisture detection in agricultural fields. Archived data have been analyzed in order to understand the SAR signal behavior of vegetated fields in comparison to bare soils. The results indicate that the sensitivity to bare fields of C and X band signatures is very close, while it changes in presence of vegetation. In particular the effect is directly proportional to amount of vegetation that in this preliminary analysis has been evaluated through the NDVI variable. After this analysis, a statistical approach has been applied to SAR images to infer the information on the soil moisture values. Several experiments have been carried out by considering only C band data, only X band data and a combination of C and X band data. For bare soils, C and X band data determine very similar results and in good agreement to ground measurements. For vegetated fields, C band data tend to underestimate soil moisture due to the vegetation attenuation, while X band data, mainly influenced by vegetation, determine very poor results. Encouraging results are obtained by the combination of C and X band data, thus indicating that X band data can be used in combination to C band data in order to compensate the effect of vegetation. © 2010 Copyright SPIE - The International Society for Optical Engineering.