This study aims to analyze problems posed by pre-service primary teachers about addition operations with fractions according to semantic structures. In addition, the study also investigated the means in which errors varied according to the semantic structures of the problems. Pre-service teachers were administered a problem posing test of four items of an addition operation with fractions. They were assigned to pose two different problems for each item related to daily situations that could only be solved with the given operations. First, problems posed were classified in the form of part-part-whole and join problems according to their semantic structures. Next, problems were analyzed according to the types of errors they involved. It was revealed that pre-service teachers generally preferred part-part-whole type of problems. Eight types of errors were determined in the problems posed. Moreover, it was identified that pre-service teachers, who used both structures as part-part-whole and join types in problems they posed, made less errors.