Hi Dr Smith, Thank you for your answer. I've run it again (see below), with the uncorrected results, and I have the same result. Any ideas? fslmaths tbss_RD_tfce_corrp_tstat2.nii.gz -mul -1 1-tbss_RD_tfce_corrp_tstat2.nii.gz fslmaths 1-tbss_RD_tfce_corrp_tstat2.nii.gz -add 1 fdr -i 1-tbss_RD_tfce_corrp_tstat2.nii.gz -m tbss_mask_3_skeleton_bin.nii.gz -q 0.05 Regards, Massih