This thesis will investigate how a commercial- and a learning computer game motivates the students and is used in math at two different schools. Introduction to the Cases: The first case deals with mathematics teaching in the 5th and 6th grade in a public school in Aarhus in a game scenario in which the computer game Torchlight 2 was used. This was used as part of a project by School at Play, which is administered by Torre N. Kjellow and Stine M. Lassen, who invented the method and they are collaborating with Thorkild Hanghøj from Aalborg University along with University College Copenhagen and VIA University College. The second case takes place at a smaller school at Funen. Having been part of the project School at Play, I was keen to study a case where I had the opportunity to examine in more details how the students were motivated to play computer using a learning game. I was allowed to spend a week in a 5th grade at a school in Funen to my study, where I used a math game called Runerod. Purpose: The primary purpose of this thesis was to investigate which elements will motivate the students in two different game scenarios, where computer games is used in mathematics education based on the theory of self-determination presented in Ryan and Rigby (2011). Method: As a methodological framework for this thesis a case study was chosen, more specifically a comparative multi-case study, due to the study design, which focuses on selected phenomena in two contexts. The epistemological positioning of this thesis is social constructivism. Results: The results of the study shows that students are clearly motivated to use computer games in math lessons. Several of the students were able to see a meaningful link between academic work and the computer games that was used in each case. The most surprising results was that students were most motivated by the need for relatedness and not the need for autonomy, even though Ryan & Rigby put this need as the most important for a person to be motivated for a computer game. Limitations and perspectives: The study addressed only two cases and the difference between the two was very large, which limits the production of knowledge in the two contexts. The time aspect and resources available were also very different for the two contexts, which can make the comparison of the two cases difficult. The study used nor further quantitative results, that might otherwise contribute to the perspective of the thesis. This choice was made to be able to handle the amount of data and focus more on qualitative empirical data and the experiences from students from the two cases.