Hi FSL experts, I did some group t-test with randomise analysis. I usually used the "Cluster-based thresholding corrected for multiple comparisons by using the null distribution of the max (across the image) cluster size". It worked very well. However, recently I did a paired t-test analysis in my new project. I made the parameter files with "Glm" wizard. However, the multiple comparison correction made me confused. I found the t value (i.e., "-c" option) I set is not corrected any more. The activated clusters I got looks very very small. For example, If we supposed t=3.5 (DF=48) means p=0.001 in my study and I used "-c 3.5" during the analysis, the "maxc" files show activated clusters are much smaller than I found in "vox" files with p=0.001 threshold. I found similar results in a 2X2 ANOVA analysis, too. Could you please do me a favor and give me some idea of it Xiaochu Zhang Ph.D Visiting Research Fellow NIH/NIDA-IRP 251 Bayview Blvd Suite 200 Baltimore MD 21224 Tel: 443-740-2619 Fax: 443-740-2734