Dear Philippe, the smooth processing step will not distinguish between sessions, and therefore it returns a single list of file names. To split them up into files per session again, you may want to do the following: At the top of your batch, insert a "Named File Selector" from BasicIO. Add as many file sets as there are sessions. Pass the file sets on to realign, slicetiming etc. (Note, that the "Named File Selector" is not constrained to NIfTI images, you may need to filter images manually in the selection dialog.) After the smooth step, insert a "File Set Split". Enter the smoothed images as files, and create as many output filesets as there are sessions. For each of them, enter the selection index from the corresponding "Named File Selector" file set. Hope this helps, Volkmar <https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=SPM;661f7458.1004>