This study investigates the diagnostic and prognostic framings of Swedishmathematics teachers regarding the difficulties experienced by studentsin mathematics learning. Collegial discussions among 65 mathematicsteachers in nine collegial groups were videotaped during a professionaldevelopment (PD) program entitled Boost for Mathematics for analysis.The results show that the diagnostic framings of the teachers weremainly attributed to the cognitive abilities of students, whereas theprognostic framings were mainly related to lesson organization suchthat students should collaborate. While the teachers emphasizecollaborate group work, they put little emphasis on how they could actin these learning situations. These results contribute to theunderstanding of Swedish mathematics teachers’ framing of students’difficulties in mathematics learning and to the role of collegialdiscussions in PD initiatives.