The dependence of flood related statistics includes mean value of annual peak flows (MAF), median value of annual peak flows (MEF), mean annual flood per unit area of drainage basin (MAF/A), median annual flood per unit area of drainage basin (MEF/A), mean annual flood divided by the mean annual precipitation (MAF/P), and median annual flood divided by the mean annual precipitation (MEF/P) on the different attributes by calculating the correlations. There were noticeable values of correlation between some of these statistics and three attributes including drainage area, mean annual precipitation and runoff coefficient. Finally, five attributes were selected to form the feature vectors and evaluate dissimilarity (similarity) between the sites for use in the regionalisation. These attributes include two geographic location attributes: longitude and latitude; and three other catchment characteristics including drainage area, mean annual precipitation and runoff coefficient. In addition, the correlation matrix was used to evaluate the independence between three latter attributes. There was not any significant correlation between these three attributes. The statistical characteristics of the considered attributes in interested sites are presented in Table 1. The attributes used to form the feature vectors were obtained from the technical reports provided by Iran WRMC.