Based on Fleivel’s theoretical framework, the subject of this paper is the study of changes in frequency of meta-cognitive activities affected by a two-month implementation of problem solving teaching in the subject of natural studies. The sample was made up of ten-year-old students. The instrument used was adapted to the student age; they were asked to state the frequency of meta-cognitive activities which they believe they applied before, during and after problem solving. The presence of meta-cognitive activities was following up in the phase of planning, monitoring and evaluation. The results show that problem solving teaching contributes to a larger presence of meta-cognitive activities in the process of planning compared to traditional teaching. In order to have a more comprehensive identification of potential meta-cognitive activities subsequent research should be directed at the use of not only this and similar instruments but also "thinking aloud" protocol. .