This special issue of the Kybernetika Journal arose from the 9th workshop on uncertainty processing, WUPES’12, held in Mariánské Lázně, Czech Republic, in September 2012. In the selection process for this special issue, we tried to capture the rich variety of the presented methodological approaches. The quality of the selected papers was judged by reviewers in accord with the usual practice of Kybernetika. After a careful selection, 7 papers were included in the special issue. There are, however, many other articles that would also have deserved to be included in this special issue.