Pedagogical Content Knowledge (PCK) has been considered to be the most important factor for identifying the role of the teacher in carrying out effective teaching. This paper examines, with respect to the components of PCK, the types of difficulties that a group of pre-service teachers encountered during the process of designing teaching activities. For this purpose, 8 pre-service teachers (4 elementary mathematics and 4 classroom teachers) are observed whilst teaching mathematics during the Teaching Practicum course and are interviewed. The study reveals that both groups of pre-service teachers had similar problems in teaching practices. Pre-service teachers experienced difficulties in determining the activities with regard to prior knowledge of the students, deciding the difficulty level of the activities and sorting them, informing students about the purpose of the activities, conducting activities according to their perceived purposes and making transitions between activities.